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Osteochondritis dissecans of the knee: Arthroscopic compression screw fixation
Arthroscopy: The Journal of Arthroscopic and Related Surgery 6(3): 179-189 Published by Raven Press, Ltd. 0 1990Arthroscopy Association of North America
Osteochondritis Dissecans of the Knee: Arthroscopic Compression Screw Fixation Lanny L. Johnson, M.D., Greg Uitvlugt, M.D., Michael D. Austin, D.O., David A. Detrisac, M.D., and Charlotte Johnson, B.S.
Summary: This article describes repair of osteochondritis dissecans of the knee by arthroscopic compression screw fixation and reports the healing response and clinical result. Diagnostic and operative arthroscopy was performed. Compression screw fixation was used. The exact operative technique varied depending on the status of the lesion. The patients were non-weight bearing for 2 months, after which a second surgery was necessary for removal of the metallic screw(s). The initial healing response was assessed by the firmness of the lesion to palpation at the second look. Subsequent x-ray evidence of healing was correlated with the clinical outcome. Ninety-four percent of the knees were determined to be initially healed at the time of the second look. Four of these apparently solid repairs subsequently loosened and required repeat surgery. Eighty-eight percent of the patients assessed their results as excellent or good after 2 years minimum follow-up. Arthroscopic compression screw fixation is an effective method of repair for mild to moderately severe cases of osteochondritis dissecans. Key Words: Osteochondritis dissecans-Internal fixation-Knee.
ommended drilling. If the articular cartilage was loose, he advocated a second tangential surgical approach through a small window under the fragment to perform curettage of the base of the lesion. When fibrous tissue protruded through the fissure, his method of treatment varied from drilling in the minor detachment to opening the lesion, debriding, and internally fixing it. He cautioned that this type of lesion is often more extensive than it appears to be on the surface. He described another lesion, one that is elevated or hinged, attached only near the intercondylar notch. In this circumstance he advocated debridement of the fibrous tissue from the base, including drilling. When significant depression of the fragment existed after fixation, Smillie advocated packing a bone graft under the fragment through the window. For internal fixation he introduced, by arthrotomy, one or more small metal nails or a screw. A second operation was routine for removal of the nail or screw. He reported cases of nail separation and migration. Smillie advocated re-
The purpose of this article is to report on an arthroscopic method of treating osteochondritis dissecans of the knee joint using internal fixation with a small metal screw. Internal fixation of osteochondritis dissecans with metal screws, pins, Kirschner wires, and bone pegs by conventional arthrotomy has been reported (l-9). Smillie outlined several principles for the surgical treatment of osteochondritis dissecans of the knee (6,7). His indication for surgery was a symptomatic patient with radiographic confirmation of osteochondritis dissecans. His operative method varied with the status of the articular fragment seen at arthrotomy. If the articular surface was intact, he recFrom the Ingham Medical Center, Lansing, MI and Michigan State University, College of Human Medicine, East Lansing, MI, U.S.A. Address correspondence and reprint requests to Dr. L. L. Johnson at 4528 S. Hagadom Road, East Lansing, MI 48823, U.S.A.
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moving loose fragments that were multiple, deformed, or necrotic and simply debriding the base of the defect. The arthroscopic surgical approach to osteochondritis dissecans has been reported by several authors (10-14). Ewing and Voto reported 72% satisfactory results with fragment removal after an average follow-up of 35 months in 29 patients, average age 25 years. Bots and Slooff reported healing of the osteochondrotic fragment in a variety of patients treated by several arthroscopic surgical methods. Ten of his patients had drilling, 11 had extraarticular grafting, 20 had intraarticular cancellous grafting with fixation of cartilage, and 13 had cortical cancellous grafting. Seven patients were in a miscellaneous group undergoing partial excision with fixation of the remaining fragment. Guhl reported a variety of arthroscopic methods directed toward preservation of the fragment. He performed various combinations of drilling, Kirschner wire fixation, and bone grafting by both retrograde and intraarticular methods. His healing rate was less than 80%. Thomson reported an arthroscopic method of fragment fixation using a metallic Herbert screw for compression fixation (14). Sixteen of 18 lesions (88%) resulted in union as determined by x-ray film. The follow-up was reported as only “four to twenty-eight months.”
MATERIALS AND METHODS A retrospective review of our private practice medical records retrieved the patients with osteochondritis dissecans treated by arthroscopic surgery and compression screw internal fixation. We report only on our patients who had compression screw fixation. Those having drilling or bone grafting were excluded and will be the subject of a subsequent report. Thirty-two patients (35 knees) with osteochondritis dissecans of the knee joint femoral condyle who had the original surgery between November 9, 1982 and January 5, 1988 were selected from the records of our private practice. The operations were performed by three surgeons (L.L.J., 26 patients, M.D.A., 7 patients, and D.A.D., 2 patients). The patient evaluations were performed by three authors (L.L.J., G.U., and C.J.). The medical record of these patients included the preoperative history, physical examination, x-ray films, operative reports, and progress notes plus Arthroscopy,
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ET AL. video tapes of the initial arthroscopic procedure and reoperations . All video tapes were reviewed to verify the written record concerning status of the lesion, surgical technique, intraoperative complications, and placement and fixation of the fragment(s). Healing was assessed at the time of second look arthroscopy by arthroscopic probing of the fragment after screw removal. The articular surface was inspected for repair and continuity. All x-ray films were reviewed. Some original xray films were on microfilm. The size of the lesion was measured on the anteroposterior film for width and on the lateral film for length. Pre- and postoperative plain-film comparisons were used to assess evidence of fragment union. Inspection was made for joint space narrowing and other evidence of degenerative arthritis. The initial follow-up was made by telephone and by a questionnaire that gave responses concerning pain, swelling, loss of motion, and loss of activities. Patients were requested to return for a follow-up examination for research purposes. The average follow-up of the entire series was 3 1/3 years. The shortest follow-up was 2 years (one patient). The longest follow-up was 6 years. The three patients lost to follow-up were last seen at 2, 6, and 9 months after surgery. Twenty-nine patients were contacted for a telephone questionnaire and 20 responded to a written questionnaire by December 1988. Fifteen patients had subsequent specific follow-up office examinations including x-ray films at an average of 3.8 years after surgery. The average age of the patients at the time of the arthroscopic treatment was 19 years. The age range was l&30 years. Nine patients were 15 years or younger in age, of whom 2 already had closed epiphyses. There were 28 male patients and 4 female patients. The right knee was involved 16 times, and the left knee 19 times. Three cases had this surgery on both knees. In two additional patients, the condition was bilateral, but the other side was not treated by this method and was not included in the study. The average time of symptoms before our surgery was 4 years. The shortest time was 13 days in a patient with sudden loosening of the fragment. The longest duration of symptoms before surgery was 16 years. The patients younger than 15 years old had failure of conservative treatment and symptoms that persisted for an average of 1.9 years before surgery.
OSTEOCHONDRITIS
DISSECANS
There was a history of trauma in 3 1% of the knees operated on. Twelve knees had some form of previous surgery for the osteochondrotic lesion. The procedures were as follows: diagnostic arthroscopy (two); fragment drilling (four); Kirschner wire fixation (two); arthrotomy (one); loose body removal and anterior cruciate ligament repair (one); Baker’s cyst removal (one); and unspecified arthroscopic procedure (one). The radiographic evaluation showed all lesions to be in the distal femoral condyles (Fig. 1). The lesion site was located medially in 30 knees and laterally in 5 knees. The lesion always involved the weightbearing joint surface to some extent. The lesion included the central weight-bearing area in 29 knees, usually with the large lesions. The epiphyses were open in eight patients. The size of the lesion was measured on the plain x-ray film. The anteroposterior length averaged 2.4 cm. The medial lateral width averaged 2.2 cm. The surgery was performed on an outpatient basis. Viewing during the procedure was from a television monitor. A simultaneous recording on video tape was stored for future review.
DIAGNOSTIC
ARTHROSCOPY
A comprehensive diagnostic arthroscopy was performed with probing (13). The osteochondrotic lesion was examined for integrity of the surface and mobility of the fragment. The lesion was placed in one of three diagnostic groups based on the diag-
FIG. 1. Anteroposterior plain-film radiograph of distal medial femoral condyle shows osteochondrotic lesion in situ.
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of lesions
Type of lesion
No.
Articular cartilage intact Fragment stable Fragment mobile with compression Articular cartilage separated (unstable) Fragment in situ Fragment hinged (partially attached) Fragment completely loose
12 0 12 19 17 2 4
nostic arthroscopic findings (Table 1). The classification status influenced the subsequent surgical technique. Those younger than age 15 had 55% intact lesions and those older than age 15 had only 9% intact lesions . The osteochondrotic fragment was in one piece in 30 knees (Fig. 2). Multiple fragments existed in five knees. The multifragmented lesion remained in situ in only one knee. Four had loose fragments. Of those, three had some portion of the multifragmented lesion still attached. One knee had all fragments detached. Other diagnostic findings were recorded. There were four cases with additional pathologic lesions. Two knees had osteochondritic defects in the lateral femoral condyle accompanying an untorn discoid lateral meniscus. No treatment was instituted for the discoid meniscus. Two cases had chondromalacia of the patella that required debridement with motorized instrumentation. In the 12 cases that had
FIG. 2. Arthroscopic view of intact osteochondritis dissecans of the femur. Probing showed the fragment to be movable.
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surgery before our internal fixation, there were minimal degenerative changes in the compartment housing the lesion. ARTHROSCOPIC
SURGICAL TECHNIQUE
We used many of Smillie’s open surgical principles in the arthroscopic method of treating osteochondritis dissecans (6-8). The arthroscopic surgical technique varied depending on the status of the articular surface and the appearance of the fragment (Table 2). When the articular cartilage was intact and the fragment was minimally compressible to probing, only a compression screw(s) was used for fixation. X-ray control was often necessary in this group because the lesion was difficult to outline by arthroscopy (Fig. 3A and B). Drilling was added to the compression screw fixation at the surgeon’s discretion in an attempt to increase the blood supply to the fragment. Lesions in which the articular cartilage was intact but more than minimal motion was detectible by probing were opened on a hinge, debrided, replaced, and internally fixed (Figs. 4-6). All lesions that had marginal fissures in the articular cartilage were treated in the same manner. Care was taken to maintain attachment at one margin of the fragment (usually medially when attached to the synovium of the intercondylar notch). In the two patients with pathologically open and hinged fragments, a debridement and reattachment was performed with internal fixation. In one, the fragment was detached and removed from the joint for reshaping. It was reinserted and fixed to the crater. In four patients the fragment was completely loose. The piece was removed from the joint, reshaped, and replaced in the crater. TECHNICAL
ASPECTS
A superficial debridement was performed on the crater and fragment with arthroscopic motorized instrumentation. This removed the interposing fiTABLE 2. Number of surgical procedures
performed
Surgical procedure
No. of knees
Compression fixation Alone With drilling Open defectidebridementxation Debridement/reattachment/fixation Loose fragment replacement/fmation
9 6 14 2 4
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ET AL. brous tissue. A minimal debridement exposed the vascularity of the crater bed, and therefore the base was not drilled (Fig. 5). Excessive debridement of the fragment and base was avoided to minimize the loss of bone substance and subsequent depression of the fragment with compression screw fixation. The orientation of the osteochondrotic fragment was such that the arthroscope was placed in the portal of the involved condyle. The osteochondrotic fragment was positioned in the crater with a probe, forceps, curette, or no. 18 spinal needle. The surgical approach for the Kirschner guide wire and subsequent screw was from the side opposite from the involved condyle. The screw was placed from the same side only in large lesions. The preliminary guide wire secured the fragment in situ and provided a means of determining by x-ray film the reduction and anticipated position of the screw placement (Fig. 3A and B). The small guide pin facilitated the passage of the cannulated screw through the soft tissues. Intraoperative x-ray control was used in 10 cases to verify the location of the internal fixation in the lesion (Fig. 3A and B). A small Kirschner wire was used for this purpose in six cases. X-ray control was used in four cases to verify screw placement. Technical difficulty can occur during screw placement and fixation. A back-and-forth motion was used when drilling over the small Kirschner wire. Intermittent withdrawing and inspecting for small metal fragments avoided cutting through the thin guide wire. An x-ray film was sometimes necessary to assure that the wire position was proper, straight, and not vulnerable to breakage with the pressure of drilling. Care was taken not to drill the screw tract too deeply, especially when the epiphyses were open. A noncannulated screw was used before 1984 in three cases. After that time, the remainder of the cases were performed with a cannulated miniature screw and instrument system. The length of the screw used was usually between 24 and 28 mm. The outside diameter of the screw head was 4 mm. The instrumentation included a cannulated calibrated drill. Tapping was not used. The screwdriver was cannulated with a hexagonal-shape male part. If the screw did not compress the fragment, it occasionally became necessary to use a longer screw, change the angle of the approach in the same point of entry, change the position, or add another screw for compression. Proper angle of approach allowed the screw head
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3A,B
FIG. 3. Intraoperative x-ray control. A: Anteroposterior x-ray film shows Kirschner wire in fragment. B: Lateral x-ray fti confms centering of wire.
to be flush with the articular surface. An attempt was made to bury the screw head below the articular surface to contact the bone, to gain compression, and to avoid protrusion that could erode the opposite tibia1 surface. A second and even third screw were used when fragment size permitted. A second screw was used in those cases in which the previous screw caused tilting of the fragment or did not control rotation. More than one screw was used in 14 cases. A washer was used in one case to gain improved mechanical purchase on a small thin piece.
FIG. 4. Arthroscopic view of movable fragment after surgical opening. The fragment was intentionally hinged on the soft tissue of the intercondylar notch.
The procedure concluded with cleansing the joint of loose debris and debriding irregular or degenerative surfaces with motorized instrumentation. The screw(s) was tightened again immediately before conclusion of the surgery. After fixation, an assessment was made of the stability of the fragment and congruity of the articular surface. Accompanying arthroscopic surgical procedures were performed. A localized anterior synovial debridement was performed in 15 knees removing the
FIG. 5. Arthroscopic view of debridement of fibrous tissue on base of crater and undersurface of the fragment.
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6A,B
FIG. 6. A: Arthroscopic _ internal fixation.
view after reduction of fragment and screw fixation. B: Radiograph of postoperative
membranous (alar) ligament and adjacent fat pad to enhance surgical exposure. A localized superficial articular cartilage debridement was performed in nine patients. Small loose bodies were removed in three knees. The operative procedures averaged 1 h and 10 min. POSTOPERATIVE
MANAGEMENT
DETERMINATION
fragment reduction and
OF HEALING OF LESION
The fragment was determined to have initial evidence of healing if it was secure to probing, after screw removal, at the time of second-look arthroscopy (average 8 weeks). Confirmation of this healing was made by postoperative radiographic evidence of trabecular union (Fig. 8). Subsequent mon-
The patients were instructed to protect the joint with non-weight-bearing crutch ambulation for 8 weeks. Only one patient was placed in a cast to ensure compliance. SECOND-LOOK ARTHROSCOPY A second procedure was performed in all cases to remove the metallic screw (Fig. 7). This provided an opportunity to assess the healing of the surface and the stability of the fragment. Fragment security was tested by palpation with a probe. This included placing the hook of the probe into the vacant screw hole for better mechanical purchase before manipulation. If the screw was not tight at the time of removal, the fragment was carefully checked for healing. If the fragment was loose, repeat fixation with a longer screw was considered. The opposite articular tibia1 surface was routinely inspected for erosion as an indication of the patient’s failure to comply with the non-weightbearing regimen. Arthroscopy,
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FIG. 7. Second-look arthroscopic view of healed fragment after screw removal. Probing of the lesion at this time confirmed healing.
OSTEOCHONDRITIS
DISSECANS
FIG. 8. Radiographic evidence of healing of lesion seen in Fig. 7.
itoring of the clinical course was necessary to provide verification of initial and radiographic evidence of union. The patients were discharged from care a minimum of 1 year after the initial surgery. RESULTS Thirty-three of the 35 knees (94%) had a solid osteochondrotic fragment to probing after screw removal at the time of the second-look arthroscopy at the g-week interval. One of the two early failures showed initial lack of healing with necrotic fragments. In this case, the tissue fragments and screws were removed. A review of the video tape of the original surgery showed that this patient had completely loose fragments of questionable quality at the time of original reattachment. The other initial failure demonstrated minimal fragment motion to probing after screw removal. Small-diameter drill holes were placed across the fragment in an attempt to complete the healing. Radiographic evidence showed that healing was never complete. The patient was asymptomatic for 3.5 years, when another surgery was necessary. The third surgery was performed with two screws, and healing occurred in 8 weeks. Four patients’ fragments appeared solid at 8 weeks by second-look arthroscopy, but experienced subsequent fragment loosening. There was radiographic confirmation of union and clinical well-being after surgery. Two patients had reinjuries resulting in subsequent arthroscopic surgery to remove fragments and debride the base of the crater. Detachment occurred in one patient without explanation. This patient had healing of the lesion af-
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ter another compression screw fixation with bone peg grafting. The fourth patient had detachment associated with an acute gouty arthritis episode, 4% years after the original fragment healing. This man weighed 350 lb. An arthroscopy was necessary to remove a shrunken, displaced fragment in the posterior compartment, followed by a synovectomy and debridement of the base of the defect. A subsequent open bone grafting procedure was performed to the crater. The patient is now healed and asymptomatic. Those patients younger than age 15 healed on first treatment attempt (9 patients, 11 knees). One patient required replacement of the screw at 4 weeks because x-ray films showed lack of juxtaposition of the screw head to the bone fragment. The fragment was solid at 8 weeks and the screw was removed. The presence of previous surgery did not adversely affect the results. Healing occurred in 91% of the 11 knees that had previous surgery, but 4 patients in this group required another surgery to confirm or produce healing. The site of the lesion did not influence the result. The medial lesions had 93% success. The lateral lesions had 100% success. The results by diagnostic type of lesion showed the intact lesions to have 92% success. Those with separated articular margins had 100% success. The multiple fragments had 83% success. The reattached loose pieces had 80% success. The least successful group based on status of the lesion was that with loose hinged fragments. One of two healed (50% success). The size of the lesion did not adversely affect the chance of success. Eight of nine cases with in-situ lesions healed with only compression screw fixation. All seven patients who underwent the compression screw fixation and drilling healed. All 14 cases healed in which the lesion was opened, debrided, and then fixed with a compression screw(s). Four of five cases healed when treated by reattachment of a loose fragment(s). This included cases in which a hinged fragment was removed, remodeled, and replaced. The failed case in this category resulted in fragment removal. The observations at second look and time of the anticipated screw removal showed that the juxtaartitular tibia1 surface was minimally eroded in eight patients who did not comply with the non-weightbearing regimen even when the screw was flush with the surface. In one case the patient did not return for 6 months, having walked on the knee. Arthroscopy,
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The erosion was to exposed bone, requiring a localized abrasion debridement and prolonged convalescence . If the screw was countersunk in the articular cartilage at the time of insertion, the second look showed the head covered with fibrous tissue. When the head protruded on an angle at the time of insertion, the protrusion still existed at the time of removal. Only one patient had an effusion or synovial reaction at second-look arthroscopy. This was the result of a residual free blood clot and not a reaction to the metal screw or joint surface irritation. Most fragments that were small and in situ were not fixed with a screw and they did not heal. In one case the fragment was small and was removed at the time of second-look arthroscopy. In another, the small fragment was fixed with a screw at the time of the second look. It healed, but a subsequent procedure was necessary for screw removal. Ten knees had depression of the fragment with screw fixation causing loss of articular congruity (Fig. 9). This did not adversely affect the patient assessment of the surgical result. Seven of these patients reported excellent results and two reported good results. One was lost to follow-up. Complications There were intraoperative complications. In two cases a Kirschner guide wire was broken. This oc-
ET AL.
cut-red with drilling over a bent wire. In each case the broken wire was retrieved. In one instance, the fragment was opened and the broken piece of wire was retrieved. There were two cases of drilling too deep, necessitating several screw insertions with redirection to gain effective compression. There were no infections, bleeding episodes, thromboembolism, or ankylosis. Reoperations All patients had a second procedure to remove the metallic screw(s). In addition, there were eight reoperations on seven knees. One was to replace an unsecured screw at 4 weeks. The fragment healed. Small loose bodies were removed arthroscopically at 1% years and at 3 years in two patients. Two patients had repeat screw fixation. One was at 1.3 years with bone peg grafting and the other was at 3 years. A diagnostic arthroscopy and localized synovectomy were performed in one patient who complained of pain with activity. Two subsequent operations were performed on one patient after 4% years. He had developed acute gouty arthritis. The fragment loosened and became necrotic. It was removed by arthroscopy with a synovectomy for the gout. A second procedure was an open bone grafting procedure to the large defect in the medial femoral condyle . Clinical result The 29 patients followed up for an average of 3V2 years reported their results by questionnaire. Eighty-eight percent of the knees (28 of 32 knees) had an excellent (14) or good (14) surgical result (Table 3). Fifty-nine percent were free of pain. Sixty-six percent had no activity modification. Seventy-live percent reported no swelling. Eighty-eight percent reported no loss of motion. Follow-up physical examination Fifteen patients (16 knees) had follow-up examinations in the office. The physical examination showed that all had a normal gait and normal rising from a chair. None had palpable tenderness. One had mild joint effusion, and the others had none. Three had compartmental crepitus, and seven had patellofemoral crepitus.
FIG. 9. Second-look arthroscopic view of articular incongruity with fragment compression. This can be avoided by minimizing debridement or by the addition of an interposition cancellous bone graft.
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Follow-up x-ray films The determination of bony union by plain x-ray film was diflicult because of irregular bony fragments (Fig. 8). The reattached osteochondrotic fragment was irregular in shape in four patients’
OSTEOCHONDRITIS
DISSECANS
TABLE 3. Clinical results Subjective result Excellent Good Fair Poor N/A Pain None With activity Occasionally Present Swelling None With activity Occasionally Present Loss of motion None In extension In flexion Activity modification None No vigorous sports No sports Prolonged walking
14 14 1 2 1 19 4 3 6 24 3 3 2 28 1 3 21 8 1 2
x-ray films. This irregularity persisted even after several years of union, so there is no well-defined termination point by radiographic assessment (Fig. IOD). In addition, a small piece of missing bone adjacent to the repaired fragment will appear as a radiolucent line on x-ray film and thereby create ditliculty in determining union. It may take several years to be certain of healing by plain x-ray film. Fifteen patients (16 knees) had follow-up x-ray films (Table 4). Two patients’ x-ray films showed a radiolucent line still present at the base of the defect. Both were asymptomatic. All other patients had radiographic evidence of union. Four of the knees showed articular incongruity at the area of the healed fragment (Fig. 10). Two showed mild degenerative arthritis by osteophyte formation. One patient had minimal joint space narrowing. Applying Hughston and Hergenroeder’s rating scale, 84% of the patients in this series ranked as excellent or good. This scale included not only the patients’ perception of their results but also examination and radiographic criteria. DISCUSSION Spontaneous healing of osteochondritis dissecans has been reported (15-17). Spontaneous healing has taken up to 7 years in nonprotected joints. For this reason, Green advocated joint protection with a
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non-weight-bearing brace or cast to reduce the time. His conservative treatment was restricted to children younger than 15 years of age. The lesions in his series were intact by x-ray film or as seen at arthrotomy. The healing time in his report was reduced to 4-11 months. The arthroscopic method outlined in this report was a reasonable treatment alternative in the symptomatic patient, considering the long time required for spontaneous healing in intact lesions and the potential for failure in detached lesions. Because our results were better when surgery was performed early in the natural history of the condition, before fragment displacement or degeneration, we agree with Smillie, who said that waiting for the separation of the loose bodies before surgical treatment “should no longer be a matter of debate” (18). We reserve fragment removal for small and degenerated pieces. Eighty-eight percent of our patients treated with arthroscopic repair of the fragment said their result was excellent or good as compared with the 72% excellent-to-good results reported by Ewing and Voto with fragment removal. In addition, Hughston and Hergenroeder’s report on open surgical treatment of osteochondritis dissecans comparing removal and repairs indicated that results were better when a repair was performed. Failure of healing was highest in detached lesions. Therefore, it is not recommended to remove attached fragments for the purpose of reshaping. In addition, fragments should remained hinged when performing debridement of the interposing fibrous tissue. The metallic screw device has the advantage of secure fixation potential, compression effect, and resistance to migration. The use of the cannulated screw after the first three cases reduced the technical difficulty of the procedure. The preliminary placement of the Kirschner wire holds the fragment and provides a conduit for percutaneous passage of the cannulated screw through the soft tissues. More than one screw was necessary in the larger lesions for fixation and to control rotation. There was no separation or migration with the screw, unlike Smillie’s series with a metal nail. When there was loss of bone because of pathological condition or surgical debridement in our series, the screw compression resulted in significant depression of the fragment. Thomson’s illustrations also show depression of a united bony fragment after Herbert compression screw fixation. The joint Arthroscopy,
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lOA,B
10 C,D
FIG. 10. Radiographic evidence of healing. A: Preoperative x-ray film. B: Postoperative x-ray film with screw in place. Note the bony defect at the margin of the fragment. C: Postoperative x-ray film after screw removal shows articular incongruity with minimal compression of the fragment, plus bony defect at the margin. D: Postoperative x-ray film after screw removal shows union of the fragment to the medial femoral condyle, but still a radiolucent area in the fragment near the joint line. The patient was asymptomatic.
contour was depressed in 10 knees in our series as a result of countersinking the fragment. This condition did not adversely affect our patients’ clinical assessment. We followed Smillie’s postoperative management of non-weight-bearing so that the opposite tibia1 surface would not be injured by the metal device (7,18). In spite of this recommendation, opposing-
TABLE 4. Radiographic 16 knees (15 patients) 14 united 2 radiolucent lines
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results
side articular injury occurred with eight noncompliant patients. This occurred even though the device was countersunk. The articular cartilage adjacent to the screw probably compressed to allow the metal screw head to erode the opposite tibia1 side. The determination of fragment healing was not reliable by arthroscopic palpation at second-look arthroscopy. Four patients had subsequent late separation of the previously “secured” fragment. Also, the determination of bony union by plain-film radiograph was difftcult because of irregular bony fragments (Figs. 8 and 1OD). In fact, two asymptomatic patients with repairs thought to be solid at surgery still had radiolucent lines at the time of follow-up. The reattached osteochondrotic fragment
OSTEOCHONDRITIS
DISSECANS
was irregular in shape in four patients’ x-ray films. This irregularity persisted even after several years of union, so there is no well-defined termination point. In addition, a small piece of missing bone adjacent to the repaired fragment will appear as a radiolucent line on an x-ray film and thereby create difficulty in determining union. It may take several years to be certain of healing by plain x-ray film. A review of illustrations in Thomson’s article showed similar difficulty in determining radiographic confirmation of union. Therefore, the best method of determining union is both absence of symptoms and failure of the fragment to loosen over time. More sophisticated tests such as computer-assisted tomography scan or magnetic resonance imaging may be necessary in the future to confirm healing. There are disadvantages to this method of treatment. The arthroscopic procedure is technically demanding, including special attention to placement of both Kirschner wire and screw. Intraoperative x-ray control may be necessary. The metallic device requires a second operation for removal, but the experience gained by the necessity of second looks did give information concerning the healing process. The screw head eroded the opposite tibia1 surface in the noncompliant patient. Future results could be improved with earlier surgical intervention in the pathological process, thus avoiding attempts at restoration of degenerated multifragmented lesions. Increased experience with the surgical procedure should avoid the technical problems of a loose screw or unsecured fragment. The addition of bone grafting in selected cases would restore the articular contour and provide a stimulus for healing. Acknowledgment:
We thank
tance with the computer
search
Andrew Pittsley of data.
for assis-
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REFERENCES 1. Gillespie HS, Day B. Bone peg fLxation in the treatment of osteochondritis dissecans of the knee joint. Clin Orthop 1979;143: 125-30. 2. Hughston JC, Hergenroeder PT, Courtenay BG. Osteochondritis dissecans of the femoral condyles. J Bone Joint Surg [Am] 1984;66: 1340-8. 3. Johnson EW, McLeod TL. Osteochondral fragments of the distal end of the femur fured with bone pegs. J Bone Joint Surg [Am] 1977;59:677-9. 4. Lindholm S, Pylkkanen P, Osterman K. Fixation of the osteochondral fragments in the knee joint. A clinical survey. Clin Orthop 1977;126:25M. 5. Lipscomb PR Jr, Lipscomb PR Sr, Bryan RS. Osteochondritis dissecans of the knee with loose fragments. Treatment by replacement and fixation with readily removed pins. J Bone Joint Surg lAm1 1978:60:235-40. Smillie IS. Inju& of the knee joint, 2nd ed. Edinburgh: E. and S. Livingstone Ltd., 1951. Smillie, IS. Treatment of osteochondritis dissecans. J Bone Joint Surg [Br] 1957;39:24&60. Johnson RP. Aabera TM. Use of retroerade bone craftinn in the treatment of osseous defects of the-lateral cond;le ofThe knee. A preliminary report of three knees in two patients. Orthopedics 1987;10:291-7. 9. Lee CK, Mercurio C. Operative treatment of osteochondritis dissecans in situ by retrograde drilling and cancellous bone graft. A preliminary report. Clin Orthop 1981;158: 12936. 10. Bots RA, Slooff TJ. Arthroscopy in the evaluation of operative treatment of osteochondrosis dissecans. Orthop Clin North Am 1979;10:685-%. 11. Ewing JW, Voto SJ. Arthroscopic surgical management of osteochondritis dissecans of the knee. Arthroscopy 1988; 4z37-40. 12. Guhl J. Arthroscopic treatment of osteochondritis dissecans: preliminary report. Orthop Clin North Am 1979;10:671-83. 13. Johnson LL. Arthroscopic surgery, principles and practice. St. Louis: CV Mosby, 1986685-97. 14. Thomson NL. Osteochondritis dissecans and osteochondral fragments managed by Herbert compression screw fixation. Clin Orthop 1987;224:71-8. 15. Green WT, Banks HH. Osteochondritis dissecans in children. J Bone Joint Surg [Am] 1953;35:26-47. 16. Van Demark RE. Osteochondritis dissecans with spontaneous healing. J Bone Joint Surg [Am] 1952;34:143-8. 17. Wiberg G. Spontaneous healing of osteochondritis dissecans in the knee joint. Acta Orthop Stand 1943;14:270. 18. Smillie IS. Injuries of the knee joint, 4th ed. Edinburgh: E. and S. Livingstone Ltd., 1975:268-330.
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Osteochondritis Dissecans of the Knee: Arthroscopic Compression Screw Fixation Lanny L. Johnson, M.D., Greg Uitvlugt, M.D., Michael D. Austin, D.O., David A. Detrisac, M.D., and Charlotte Johnson, B.S.
Summary: This article describes repair of osteochondritis dissecans of the knee by arthroscopic compression screw fixation and reports the healing response and clinical result. Diagnostic and operative arthroscopy was performed. Compression screw fixation was used. The exact operative technique varied depending on the status of the lesion. The patients were non-weight bearing for 2 months, after which a second surgery was necessary for removal of the metallic screw(s). The initial healing response was assessed by the firmness of the lesion to palpation at the second look. Subsequent x-ray evidence of healing was correlated with the clinical outcome. Ninety-four percent of the knees were determined to be initially healed at the time of the second look. Four of these apparently solid repairs subsequently loosened and required repeat surgery. Eighty-eight percent of the patients assessed their results as excellent or good after 2 years minimum follow-up. Arthroscopic compression screw fixation is an effective method of repair for mild to moderately severe cases of osteochondritis dissecans. Key Words: Osteochondritis dissecans-Internal fixation-Knee.
ommended drilling. If the articular cartilage was loose, he advocated a second tangential surgical approach through a small window under the fragment to perform curettage of the base of the lesion. When fibrous tissue protruded through the fissure, his method of treatment varied from drilling in the minor detachment to opening the lesion, debriding, and internally fixing it. He cautioned that this type of lesion is often more extensive than it appears to be on the surface. He described another lesion, one that is elevated or hinged, attached only near the intercondylar notch. In this circumstance he advocated debridement of the fibrous tissue from the base, including drilling. When significant depression of the fragment existed after fixation, Smillie advocated packing a bone graft under the fragment through the window. For internal fixation he introduced, by arthrotomy, one or more small metal nails or a screw. A second operation was routine for removal of the nail or screw. He reported cases of nail separation and migration. Smillie advocated re-
The purpose of this article is to report on an arthroscopic method of treating osteochondritis dissecans of the knee joint using internal fixation with a small metal screw. Internal fixation of osteochondritis dissecans with metal screws, pins, Kirschner wires, and bone pegs by conventional arthrotomy has been reported (l-9). Smillie outlined several principles for the surgical treatment of osteochondritis dissecans of the knee (6,7). His indication for surgery was a symptomatic patient with radiographic confirmation of osteochondritis dissecans. His operative method varied with the status of the articular fragment seen at arthrotomy. If the articular surface was intact, he recFrom the Ingham Medical Center, Lansing, MI and Michigan State University, College of Human Medicine, East Lansing, MI, U.S.A. Address correspondence and reprint requests to Dr. L. L. Johnson at 4528 S. Hagadom Road, East Lansing, MI 48823, U.S.A.
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moving loose fragments that were multiple, deformed, or necrotic and simply debriding the base of the defect. The arthroscopic surgical approach to osteochondritis dissecans has been reported by several authors (10-14). Ewing and Voto reported 72% satisfactory results with fragment removal after an average follow-up of 35 months in 29 patients, average age 25 years. Bots and Slooff reported healing of the osteochondrotic fragment in a variety of patients treated by several arthroscopic surgical methods. Ten of his patients had drilling, 11 had extraarticular grafting, 20 had intraarticular cancellous grafting with fixation of cartilage, and 13 had cortical cancellous grafting. Seven patients were in a miscellaneous group undergoing partial excision with fixation of the remaining fragment. Guhl reported a variety of arthroscopic methods directed toward preservation of the fragment. He performed various combinations of drilling, Kirschner wire fixation, and bone grafting by both retrograde and intraarticular methods. His healing rate was less than 80%. Thomson reported an arthroscopic method of fragment fixation using a metallic Herbert screw for compression fixation (14). Sixteen of 18 lesions (88%) resulted in union as determined by x-ray film. The follow-up was reported as only “four to twenty-eight months.”
MATERIALS AND METHODS A retrospective review of our private practice medical records retrieved the patients with osteochondritis dissecans treated by arthroscopic surgery and compression screw internal fixation. We report only on our patients who had compression screw fixation. Those having drilling or bone grafting were excluded and will be the subject of a subsequent report. Thirty-two patients (35 knees) with osteochondritis dissecans of the knee joint femoral condyle who had the original surgery between November 9, 1982 and January 5, 1988 were selected from the records of our private practice. The operations were performed by three surgeons (L.L.J., 26 patients, M.D.A., 7 patients, and D.A.D., 2 patients). The patient evaluations were performed by three authors (L.L.J., G.U., and C.J.). The medical record of these patients included the preoperative history, physical examination, x-ray films, operative reports, and progress notes plus Arthroscopy,
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ET AL. video tapes of the initial arthroscopic procedure and reoperations . All video tapes were reviewed to verify the written record concerning status of the lesion, surgical technique, intraoperative complications, and placement and fixation of the fragment(s). Healing was assessed at the time of second look arthroscopy by arthroscopic probing of the fragment after screw removal. The articular surface was inspected for repair and continuity. All x-ray films were reviewed. Some original xray films were on microfilm. The size of the lesion was measured on the anteroposterior film for width and on the lateral film for length. Pre- and postoperative plain-film comparisons were used to assess evidence of fragment union. Inspection was made for joint space narrowing and other evidence of degenerative arthritis. The initial follow-up was made by telephone and by a questionnaire that gave responses concerning pain, swelling, loss of motion, and loss of activities. Patients were requested to return for a follow-up examination for research purposes. The average follow-up of the entire series was 3 1/3 years. The shortest follow-up was 2 years (one patient). The longest follow-up was 6 years. The three patients lost to follow-up were last seen at 2, 6, and 9 months after surgery. Twenty-nine patients were contacted for a telephone questionnaire and 20 responded to a written questionnaire by December 1988. Fifteen patients had subsequent specific follow-up office examinations including x-ray films at an average of 3.8 years after surgery. The average age of the patients at the time of the arthroscopic treatment was 19 years. The age range was l&30 years. Nine patients were 15 years or younger in age, of whom 2 already had closed epiphyses. There were 28 male patients and 4 female patients. The right knee was involved 16 times, and the left knee 19 times. Three cases had this surgery on both knees. In two additional patients, the condition was bilateral, but the other side was not treated by this method and was not included in the study. The average time of symptoms before our surgery was 4 years. The shortest time was 13 days in a patient with sudden loosening of the fragment. The longest duration of symptoms before surgery was 16 years. The patients younger than 15 years old had failure of conservative treatment and symptoms that persisted for an average of 1.9 years before surgery.
OSTEOCHONDRITIS
DISSECANS
There was a history of trauma in 3 1% of the knees operated on. Twelve knees had some form of previous surgery for the osteochondrotic lesion. The procedures were as follows: diagnostic arthroscopy (two); fragment drilling (four); Kirschner wire fixation (two); arthrotomy (one); loose body removal and anterior cruciate ligament repair (one); Baker’s cyst removal (one); and unspecified arthroscopic procedure (one). The radiographic evaluation showed all lesions to be in the distal femoral condyles (Fig. 1). The lesion site was located medially in 30 knees and laterally in 5 knees. The lesion always involved the weightbearing joint surface to some extent. The lesion included the central weight-bearing area in 29 knees, usually with the large lesions. The epiphyses were open in eight patients. The size of the lesion was measured on the plain x-ray film. The anteroposterior length averaged 2.4 cm. The medial lateral width averaged 2.2 cm. The surgery was performed on an outpatient basis. Viewing during the procedure was from a television monitor. A simultaneous recording on video tape was stored for future review.
DIAGNOSTIC
ARTHROSCOPY
A comprehensive diagnostic arthroscopy was performed with probing (13). The osteochondrotic lesion was examined for integrity of the surface and mobility of the fragment. The lesion was placed in one of three diagnostic groups based on the diag-
FIG. 1. Anteroposterior plain-film radiograph of distal medial femoral condyle shows osteochondrotic lesion in situ.
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of lesions
Type of lesion
No.
Articular cartilage intact Fragment stable Fragment mobile with compression Articular cartilage separated (unstable) Fragment in situ Fragment hinged (partially attached) Fragment completely loose
12 0 12 19 17 2 4
nostic arthroscopic findings (Table 1). The classification status influenced the subsequent surgical technique. Those younger than age 15 had 55% intact lesions and those older than age 15 had only 9% intact lesions . The osteochondrotic fragment was in one piece in 30 knees (Fig. 2). Multiple fragments existed in five knees. The multifragmented lesion remained in situ in only one knee. Four had loose fragments. Of those, three had some portion of the multifragmented lesion still attached. One knee had all fragments detached. Other diagnostic findings were recorded. There were four cases with additional pathologic lesions. Two knees had osteochondritic defects in the lateral femoral condyle accompanying an untorn discoid lateral meniscus. No treatment was instituted for the discoid meniscus. Two cases had chondromalacia of the patella that required debridement with motorized instrumentation. In the 12 cases that had
FIG. 2. Arthroscopic view of intact osteochondritis dissecans of the femur. Probing showed the fragment to be movable.
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surgery before our internal fixation, there were minimal degenerative changes in the compartment housing the lesion. ARTHROSCOPIC
SURGICAL TECHNIQUE
We used many of Smillie’s open surgical principles in the arthroscopic method of treating osteochondritis dissecans (6-8). The arthroscopic surgical technique varied depending on the status of the articular surface and the appearance of the fragment (Table 2). When the articular cartilage was intact and the fragment was minimally compressible to probing, only a compression screw(s) was used for fixation. X-ray control was often necessary in this group because the lesion was difficult to outline by arthroscopy (Fig. 3A and B). Drilling was added to the compression screw fixation at the surgeon’s discretion in an attempt to increase the blood supply to the fragment. Lesions in which the articular cartilage was intact but more than minimal motion was detectible by probing were opened on a hinge, debrided, replaced, and internally fixed (Figs. 4-6). All lesions that had marginal fissures in the articular cartilage were treated in the same manner. Care was taken to maintain attachment at one margin of the fragment (usually medially when attached to the synovium of the intercondylar notch). In the two patients with pathologically open and hinged fragments, a debridement and reattachment was performed with internal fixation. In one, the fragment was detached and removed from the joint for reshaping. It was reinserted and fixed to the crater. In four patients the fragment was completely loose. The piece was removed from the joint, reshaped, and replaced in the crater. TECHNICAL
ASPECTS
A superficial debridement was performed on the crater and fragment with arthroscopic motorized instrumentation. This removed the interposing fiTABLE 2. Number of surgical procedures
performed
Surgical procedure
No. of knees
Compression fixation Alone With drilling Open defectidebridementxation Debridement/reattachment/fixation Loose fragment replacement/fmation
9 6 14 2 4
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ET AL. brous tissue. A minimal debridement exposed the vascularity of the crater bed, and therefore the base was not drilled (Fig. 5). Excessive debridement of the fragment and base was avoided to minimize the loss of bone substance and subsequent depression of the fragment with compression screw fixation. The orientation of the osteochondrotic fragment was such that the arthroscope was placed in the portal of the involved condyle. The osteochondrotic fragment was positioned in the crater with a probe, forceps, curette, or no. 18 spinal needle. The surgical approach for the Kirschner guide wire and subsequent screw was from the side opposite from the involved condyle. The screw was placed from the same side only in large lesions. The preliminary guide wire secured the fragment in situ and provided a means of determining by x-ray film the reduction and anticipated position of the screw placement (Fig. 3A and B). The small guide pin facilitated the passage of the cannulated screw through the soft tissues. Intraoperative x-ray control was used in 10 cases to verify the location of the internal fixation in the lesion (Fig. 3A and B). A small Kirschner wire was used for this purpose in six cases. X-ray control was used in four cases to verify screw placement. Technical difficulty can occur during screw placement and fixation. A back-and-forth motion was used when drilling over the small Kirschner wire. Intermittent withdrawing and inspecting for small metal fragments avoided cutting through the thin guide wire. An x-ray film was sometimes necessary to assure that the wire position was proper, straight, and not vulnerable to breakage with the pressure of drilling. Care was taken not to drill the screw tract too deeply, especially when the epiphyses were open. A noncannulated screw was used before 1984 in three cases. After that time, the remainder of the cases were performed with a cannulated miniature screw and instrument system. The length of the screw used was usually between 24 and 28 mm. The outside diameter of the screw head was 4 mm. The instrumentation included a cannulated calibrated drill. Tapping was not used. The screwdriver was cannulated with a hexagonal-shape male part. If the screw did not compress the fragment, it occasionally became necessary to use a longer screw, change the angle of the approach in the same point of entry, change the position, or add another screw for compression. Proper angle of approach allowed the screw head
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3A,B
FIG. 3. Intraoperative x-ray control. A: Anteroposterior x-ray film shows Kirschner wire in fragment. B: Lateral x-ray fti confms centering of wire.
to be flush with the articular surface. An attempt was made to bury the screw head below the articular surface to contact the bone, to gain compression, and to avoid protrusion that could erode the opposite tibia1 surface. A second and even third screw were used when fragment size permitted. A second screw was used in those cases in which the previous screw caused tilting of the fragment or did not control rotation. More than one screw was used in 14 cases. A washer was used in one case to gain improved mechanical purchase on a small thin piece.
FIG. 4. Arthroscopic view of movable fragment after surgical opening. The fragment was intentionally hinged on the soft tissue of the intercondylar notch.
The procedure concluded with cleansing the joint of loose debris and debriding irregular or degenerative surfaces with motorized instrumentation. The screw(s) was tightened again immediately before conclusion of the surgery. After fixation, an assessment was made of the stability of the fragment and congruity of the articular surface. Accompanying arthroscopic surgical procedures were performed. A localized anterior synovial debridement was performed in 15 knees removing the
FIG. 5. Arthroscopic view of debridement of fibrous tissue on base of crater and undersurface of the fragment.
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6A,B
FIG. 6. A: Arthroscopic _ internal fixation.
view after reduction of fragment and screw fixation. B: Radiograph of postoperative
membranous (alar) ligament and adjacent fat pad to enhance surgical exposure. A localized superficial articular cartilage debridement was performed in nine patients. Small loose bodies were removed in three knees. The operative procedures averaged 1 h and 10 min. POSTOPERATIVE
MANAGEMENT
DETERMINATION
fragment reduction and
OF HEALING OF LESION
The fragment was determined to have initial evidence of healing if it was secure to probing, after screw removal, at the time of second-look arthroscopy (average 8 weeks). Confirmation of this healing was made by postoperative radiographic evidence of trabecular union (Fig. 8). Subsequent mon-
The patients were instructed to protect the joint with non-weight-bearing crutch ambulation for 8 weeks. Only one patient was placed in a cast to ensure compliance. SECOND-LOOK ARTHROSCOPY A second procedure was performed in all cases to remove the metallic screw (Fig. 7). This provided an opportunity to assess the healing of the surface and the stability of the fragment. Fragment security was tested by palpation with a probe. This included placing the hook of the probe into the vacant screw hole for better mechanical purchase before manipulation. If the screw was not tight at the time of removal, the fragment was carefully checked for healing. If the fragment was loose, repeat fixation with a longer screw was considered. The opposite articular tibia1 surface was routinely inspected for erosion as an indication of the patient’s failure to comply with the non-weightbearing regimen. Arthroscopy,
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FIG. 7. Second-look arthroscopic view of healed fragment after screw removal. Probing of the lesion at this time confirmed healing.
OSTEOCHONDRITIS
DISSECANS
FIG. 8. Radiographic evidence of healing of lesion seen in Fig. 7.
itoring of the clinical course was necessary to provide verification of initial and radiographic evidence of union. The patients were discharged from care a minimum of 1 year after the initial surgery. RESULTS Thirty-three of the 35 knees (94%) had a solid osteochondrotic fragment to probing after screw removal at the time of the second-look arthroscopy at the g-week interval. One of the two early failures showed initial lack of healing with necrotic fragments. In this case, the tissue fragments and screws were removed. A review of the video tape of the original surgery showed that this patient had completely loose fragments of questionable quality at the time of original reattachment. The other initial failure demonstrated minimal fragment motion to probing after screw removal. Small-diameter drill holes were placed across the fragment in an attempt to complete the healing. Radiographic evidence showed that healing was never complete. The patient was asymptomatic for 3.5 years, when another surgery was necessary. The third surgery was performed with two screws, and healing occurred in 8 weeks. Four patients’ fragments appeared solid at 8 weeks by second-look arthroscopy, but experienced subsequent fragment loosening. There was radiographic confirmation of union and clinical well-being after surgery. Two patients had reinjuries resulting in subsequent arthroscopic surgery to remove fragments and debride the base of the crater. Detachment occurred in one patient without explanation. This patient had healing of the lesion af-
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ter another compression screw fixation with bone peg grafting. The fourth patient had detachment associated with an acute gouty arthritis episode, 4% years after the original fragment healing. This man weighed 350 lb. An arthroscopy was necessary to remove a shrunken, displaced fragment in the posterior compartment, followed by a synovectomy and debridement of the base of the defect. A subsequent open bone grafting procedure was performed to the crater. The patient is now healed and asymptomatic. Those patients younger than age 15 healed on first treatment attempt (9 patients, 11 knees). One patient required replacement of the screw at 4 weeks because x-ray films showed lack of juxtaposition of the screw head to the bone fragment. The fragment was solid at 8 weeks and the screw was removed. The presence of previous surgery did not adversely affect the results. Healing occurred in 91% of the 11 knees that had previous surgery, but 4 patients in this group required another surgery to confirm or produce healing. The site of the lesion did not influence the result. The medial lesions had 93% success. The lateral lesions had 100% success. The results by diagnostic type of lesion showed the intact lesions to have 92% success. Those with separated articular margins had 100% success. The multiple fragments had 83% success. The reattached loose pieces had 80% success. The least successful group based on status of the lesion was that with loose hinged fragments. One of two healed (50% success). The size of the lesion did not adversely affect the chance of success. Eight of nine cases with in-situ lesions healed with only compression screw fixation. All seven patients who underwent the compression screw fixation and drilling healed. All 14 cases healed in which the lesion was opened, debrided, and then fixed with a compression screw(s). Four of five cases healed when treated by reattachment of a loose fragment(s). This included cases in which a hinged fragment was removed, remodeled, and replaced. The failed case in this category resulted in fragment removal. The observations at second look and time of the anticipated screw removal showed that the juxtaartitular tibia1 surface was minimally eroded in eight patients who did not comply with the non-weightbearing regimen even when the screw was flush with the surface. In one case the patient did not return for 6 months, having walked on the knee. Arthroscopy,
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The erosion was to exposed bone, requiring a localized abrasion debridement and prolonged convalescence . If the screw was countersunk in the articular cartilage at the time of insertion, the second look showed the head covered with fibrous tissue. When the head protruded on an angle at the time of insertion, the protrusion still existed at the time of removal. Only one patient had an effusion or synovial reaction at second-look arthroscopy. This was the result of a residual free blood clot and not a reaction to the metal screw or joint surface irritation. Most fragments that were small and in situ were not fixed with a screw and they did not heal. In one case the fragment was small and was removed at the time of second-look arthroscopy. In another, the small fragment was fixed with a screw at the time of the second look. It healed, but a subsequent procedure was necessary for screw removal. Ten knees had depression of the fragment with screw fixation causing loss of articular congruity (Fig. 9). This did not adversely affect the patient assessment of the surgical result. Seven of these patients reported excellent results and two reported good results. One was lost to follow-up. Complications There were intraoperative complications. In two cases a Kirschner guide wire was broken. This oc-
ET AL.
cut-red with drilling over a bent wire. In each case the broken wire was retrieved. In one instance, the fragment was opened and the broken piece of wire was retrieved. There were two cases of drilling too deep, necessitating several screw insertions with redirection to gain effective compression. There were no infections, bleeding episodes, thromboembolism, or ankylosis. Reoperations All patients had a second procedure to remove the metallic screw(s). In addition, there were eight reoperations on seven knees. One was to replace an unsecured screw at 4 weeks. The fragment healed. Small loose bodies were removed arthroscopically at 1% years and at 3 years in two patients. Two patients had repeat screw fixation. One was at 1.3 years with bone peg grafting and the other was at 3 years. A diagnostic arthroscopy and localized synovectomy were performed in one patient who complained of pain with activity. Two subsequent operations were performed on one patient after 4% years. He had developed acute gouty arthritis. The fragment loosened and became necrotic. It was removed by arthroscopy with a synovectomy for the gout. A second procedure was an open bone grafting procedure to the large defect in the medial femoral condyle . Clinical result The 29 patients followed up for an average of 3V2 years reported their results by questionnaire. Eighty-eight percent of the knees (28 of 32 knees) had an excellent (14) or good (14) surgical result (Table 3). Fifty-nine percent were free of pain. Sixty-six percent had no activity modification. Seventy-live percent reported no swelling. Eighty-eight percent reported no loss of motion. Follow-up physical examination Fifteen patients (16 knees) had follow-up examinations in the office. The physical examination showed that all had a normal gait and normal rising from a chair. None had palpable tenderness. One had mild joint effusion, and the others had none. Three had compartmental crepitus, and seven had patellofemoral crepitus.
FIG. 9. Second-look arthroscopic view of articular incongruity with fragment compression. This can be avoided by minimizing debridement or by the addition of an interposition cancellous bone graft.
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Follow-up x-ray films The determination of bony union by plain x-ray film was diflicult because of irregular bony fragments (Fig. 8). The reattached osteochondrotic fragment was irregular in shape in four patients’
OSTEOCHONDRITIS
DISSECANS
TABLE 3. Clinical results Subjective result Excellent Good Fair Poor N/A Pain None With activity Occasionally Present Swelling None With activity Occasionally Present Loss of motion None In extension In flexion Activity modification None No vigorous sports No sports Prolonged walking
14 14 1 2 1 19 4 3 6 24 3 3 2 28 1 3 21 8 1 2
x-ray films. This irregularity persisted even after several years of union, so there is no well-defined termination point by radiographic assessment (Fig. IOD). In addition, a small piece of missing bone adjacent to the repaired fragment will appear as a radiolucent line on x-ray film and thereby create ditliculty in determining union. It may take several years to be certain of healing by plain x-ray film. Fifteen patients (16 knees) had follow-up x-ray films (Table 4). Two patients’ x-ray films showed a radiolucent line still present at the base of the defect. Both were asymptomatic. All other patients had radiographic evidence of union. Four of the knees showed articular incongruity at the area of the healed fragment (Fig. 10). Two showed mild degenerative arthritis by osteophyte formation. One patient had minimal joint space narrowing. Applying Hughston and Hergenroeder’s rating scale, 84% of the patients in this series ranked as excellent or good. This scale included not only the patients’ perception of their results but also examination and radiographic criteria. DISCUSSION Spontaneous healing of osteochondritis dissecans has been reported (15-17). Spontaneous healing has taken up to 7 years in nonprotected joints. For this reason, Green advocated joint protection with a
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non-weight-bearing brace or cast to reduce the time. His conservative treatment was restricted to children younger than 15 years of age. The lesions in his series were intact by x-ray film or as seen at arthrotomy. The healing time in his report was reduced to 4-11 months. The arthroscopic method outlined in this report was a reasonable treatment alternative in the symptomatic patient, considering the long time required for spontaneous healing in intact lesions and the potential for failure in detached lesions. Because our results were better when surgery was performed early in the natural history of the condition, before fragment displacement or degeneration, we agree with Smillie, who said that waiting for the separation of the loose bodies before surgical treatment “should no longer be a matter of debate” (18). We reserve fragment removal for small and degenerated pieces. Eighty-eight percent of our patients treated with arthroscopic repair of the fragment said their result was excellent or good as compared with the 72% excellent-to-good results reported by Ewing and Voto with fragment removal. In addition, Hughston and Hergenroeder’s report on open surgical treatment of osteochondritis dissecans comparing removal and repairs indicated that results were better when a repair was performed. Failure of healing was highest in detached lesions. Therefore, it is not recommended to remove attached fragments for the purpose of reshaping. In addition, fragments should remained hinged when performing debridement of the interposing fibrous tissue. The metallic screw device has the advantage of secure fixation potential, compression effect, and resistance to migration. The use of the cannulated screw after the first three cases reduced the technical difficulty of the procedure. The preliminary placement of the Kirschner wire holds the fragment and provides a conduit for percutaneous passage of the cannulated screw through the soft tissues. More than one screw was necessary in the larger lesions for fixation and to control rotation. There was no separation or migration with the screw, unlike Smillie’s series with a metal nail. When there was loss of bone because of pathological condition or surgical debridement in our series, the screw compression resulted in significant depression of the fragment. Thomson’s illustrations also show depression of a united bony fragment after Herbert compression screw fixation. The joint Arthroscopy,
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lOA,B
10 C,D
FIG. 10. Radiographic evidence of healing. A: Preoperative x-ray film. B: Postoperative x-ray film with screw in place. Note the bony defect at the margin of the fragment. C: Postoperative x-ray film after screw removal shows articular incongruity with minimal compression of the fragment, plus bony defect at the margin. D: Postoperative x-ray film after screw removal shows union of the fragment to the medial femoral condyle, but still a radiolucent area in the fragment near the joint line. The patient was asymptomatic.
contour was depressed in 10 knees in our series as a result of countersinking the fragment. This condition did not adversely affect our patients’ clinical assessment. We followed Smillie’s postoperative management of non-weight-bearing so that the opposite tibia1 surface would not be injured by the metal device (7,18). In spite of this recommendation, opposing-
TABLE 4. Radiographic 16 knees (15 patients) 14 united 2 radiolucent lines
Arthroscopy. Vol. 6, No. 3, 1990
results
side articular injury occurred with eight noncompliant patients. This occurred even though the device was countersunk. The articular cartilage adjacent to the screw probably compressed to allow the metal screw head to erode the opposite tibia1 side. The determination of fragment healing was not reliable by arthroscopic palpation at second-look arthroscopy. Four patients had subsequent late separation of the previously “secured” fragment. Also, the determination of bony union by plain-film radiograph was difftcult because of irregular bony fragments (Figs. 8 and 1OD). In fact, two asymptomatic patients with repairs thought to be solid at surgery still had radiolucent lines at the time of follow-up. The reattached osteochondrotic fragment
OSTEOCHONDRITIS
DISSECANS
was irregular in shape in four patients’ x-ray films. This irregularity persisted even after several years of union, so there is no well-defined termination point. In addition, a small piece of missing bone adjacent to the repaired fragment will appear as a radiolucent line on an x-ray film and thereby create difficulty in determining union. It may take several years to be certain of healing by plain x-ray film. A review of illustrations in Thomson’s article showed similar difficulty in determining radiographic confirmation of union. Therefore, the best method of determining union is both absence of symptoms and failure of the fragment to loosen over time. More sophisticated tests such as computer-assisted tomography scan or magnetic resonance imaging may be necessary in the future to confirm healing. There are disadvantages to this method of treatment. The arthroscopic procedure is technically demanding, including special attention to placement of both Kirschner wire and screw. Intraoperative x-ray control may be necessary. The metallic device requires a second operation for removal, but the experience gained by the necessity of second looks did give information concerning the healing process. The screw head eroded the opposite tibia1 surface in the noncompliant patient. Future results could be improved with earlier surgical intervention in the pathological process, thus avoiding attempts at restoration of degenerated multifragmented lesions. Increased experience with the surgical procedure should avoid the technical problems of a loose screw or unsecured fragment. The addition of bone grafting in selected cases would restore the articular contour and provide a stimulus for healing. Acknowledgment:
We thank
tance with the computer
search
Andrew Pittsley of data.
for assis-
OF THE KNEE
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Arthroscopy,
Vol. 6, No. 3, 1990