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Alterations of the extensor apparatus after anterior cruciate ligament reconstruction using the medial third of the patellar tendon
Alterations of the Extensor Apparatus After Anterior Cruciate Ligament Reconstruction Using the Medial Third of the Patellar Tendon Ulf G. Moebius, M.D., Anastasios D. Georgoulis, M.D., Christos D. Papageorgiou, M.D., Anastasios Papadonikolakis, M.D., Julian Rossis, M.D., and Panayotis N. Soucacos, M.D.
Purpose: The objective of this study was the ultrasound evaluation of the donor defect of the patellar tendon (PT) and the radiologic evaluation of the patella after harvesting of the medial third as a bone–patella tendon– bone (BPTB) graft for anterior cruciate ligament (ACL) reconstruction. Type of Study: This was a cohort study. Methods: In 45 patients who had ACL reconstruction, the extensor apparatus of the donor side was studied using ultrasound cross-sections and radiographs (anteroposterior, lateral, and a tangential view of the patella) 3 to 70 months postoperatively. Patients were divided into two groups. The early postoperative group (3 to 30 months postoperative) consisted of 27 patients (group A) and the late postoperative group (31 to 70 months postoperative) consisted of 18 patients (group B). The healthy contralateral extensor apparatus was used as control. Results: In group A, the standard ultrasound cross-section area of the PT increased by 20.48%, whereas in group B, it decreased by 4.88%. In group A, the patellar height was decreased by 9.21% in the donor side compared with the control. In group B, the patellar height was decreased by 7.02%. In group A, the Merchant’s congruence angle increased by 11.59°, and for group B, this angle increased by 3.82°. This finding indicated that, after the 30th postoperative month, lateral displacement of the patella was not statistically significant (P ⫽ .38). In addition, no significant differences were found in the lateral patellofemoral angle in either group. Conclusions: Our study indicates that the tendon defect is always healed and the final tendon cross-section area is 95% of the contralateral after the 30th postoperative month. In addition, there was a nonsignificant slight lateral displacement of the patella. In contrast, other studies found shown that there is a slight medial displacement of the PT after using the central third as a BPTB graft. Key Words: Anterior cruciate ligament—Medial third BPTB graft—Patellar alignment—Harvesting defect healing—Ultrasound evaluation.
A
s a bone–patellar tendon– bone (BPTB) graft for anterior cruciate ligament (ACL) reconstruction, one third of the patellar tendon (PT) is widely used because of the biomechanical characteristics of the graft and the stable fixation of the bone plugs that allow early mobilization.1-3 This technique has many
From the Department of Orthopaedic Surgery, Medical School, University of Ioannina, Ioannina, Greece. Address correspondence and reprint requests to Anastasios D. Georgoulis, M.D., Department of Orthopaedic Surgery, Medical School of Ioannina, PO Box 1042, Ioannina 45 110, Greece. E-mail: [email protected] © 2001 by the Arthroscopy Association of North America 0749-8063/01/1709-2583$35.00/0 doi:10.1053/jars.2001.25957
advantages including graft strength similar to the original ACL ligament, but there are disadvantages that can reduce successful patient outcome. Some of these disadvantages are complications and problems related to the donor-site defect and its healing process. Complications include patella fracture, PT avulsion, lateral or medial subluxation of the patella, and patella baja.4-6 The healing process of the donor defect has been studied mainly after BPTB harvesting of the central third of the PT. Some investigators, using ultrasound and magnetic resonance imaging, have reported hypertrophy of the PT postoperatively and healing of the donor defect with scar tissue.7-9 Indeed, in animal studies, the donor defect is replaced with scar tissue
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that does not assume the histologic and biomechanical properties of the neighboring tendon tissue.10-12 Furthermore, Nixon et al.9 found scar tissue in a biopsy specimen from the donor site of the PT that was nearly identical to normal tendon tissue. Karns et al.,13 using the donor defect tissue in revision ACL surgery, also found a normal histologic picture 4 years after primary ACL reconstruction. However, other investigators have reported partial or no healing of the defect 2 years postoperatively.14,15 Possibly, the different reported results are related to the closing or not of the peritendon in the donor site.12 Another question remaining is whether harvesting of the BPTB graft alters the patella position in the femoral trochlea, causing either patella baja, or sideways displacement. Many authors refer to the harvesting procedure as the cause of shrinkage of the PT or as a partial cause of infrapatellar contracture syndrome.5,16-18 Arthroscopically detected changes of the patellofemoral joint have been reported as a result of alteration to the extensor mechanism after PT harvesting.19 In a study examining the alignment of the patella after harvesting of the central third of the PT,20 a change in the Merchant’s angle of about 4.7° was found in a 2-year follow-up period. This finding indicated that, while the lateral patellofemoral angle remains the same, medial relocation of the patella occurs. Most studies of the extensor mechanism are focused on the alterations after harvesting the central third of the PT. There have been only a few reports on changes of the extensor mechanism after use of the medial third of the PT.16,21,22 The purpose of our study was the ultrasound examination of the PT donor defect and the radiologic investigation of the patella after harvesting of the medial third as BPTB graft for ACL reconstruction. METHODS Forty-five patients (34 men and 11 women; mean age, 26.1 years) who had undergone ACL reconstruction using the medial third of the PT were re-examined 3 months to 6 years postoperatively (mean interval, 26.6 months). Patients with procedures to the contralateral knee joint or any lesion of the extensor mechanism were excluded from this cohort study. In a preliminary study, large variations were found during the first 30 postoperative months. After the 30th postoperative month, the Merchant’s congruence angle23 and ultrasound cross-section area remained unchanged. Thus, in our study the patients were di-
vided into 2 groups; 27 patients (group A) were examined 3 to 30 months postoperatively (mean interval, 10.3 months) and 18 patients (group B) were examined 31 to 70 months postoperatively (mean interval, 49.2 months). In all patients, ACL reconstruction was performed using the press-fit technique as described by Hertel et al.24-26 According to this technique, the medial third of the patella is used as a graft because of the flag-like shape of the bone block harvested from the patella. The peritenon was carefully sutured after the harvesting procedure. Furthermore, the bone defects of the patella and the tibia were always filled either by autograft or allograft. The postoperative rehabilitation program was as follows. Isometric training of the thigh muscles was started on the first postoperative day; movement of the knee joint was permitted from 0° to 90° of flexion during the first 2 weeks; walking with the aid of crutches and using an extension brace for 4 weeks; after postoperative week 4, step-wise weight bearing was commenced, and by postoperative week 6, full weight bearing was allowed. After 2 months, jogging was permitted. Before participation in sporting activities, proprioception training was carried out. The PT was examined using a standard ultrasound device with a 7.5-MHz high-resolution linear transducer. The knee joint was flexed at 90° to ensure adequate tension of the tendon. The tibial tuberosity was palpated, and the lower edge of the transducer was attached to the upper edge of the tuberosity. Using this protocol, a standard sagittal cross-section, 0.5 cm above the upper edge of the tuberositas tibiae, was taken and measured. The images were developed on film. To ensure that the PT of the contralateral knee could be used as control, we examined the PT of 15 volunteers with intact knee joints. No significant differences were found between the right and the left PT crosssection area in the volunteers. The width and thickness of the PT could not be accurately measured because these parameters are affected during examination by pressure of the ultrasound transducer on the tendon. The patients’ knees were also evaluated using lateral radiographs of the knee joint at 30° of flexion and tangential radiographs of the patella. The ultrasound images were digitized so as to reduce the examination time and leave the ultrasound system free for hospital use. Radiographs were also digitized and then processed using an image-processing program (Adobe Photoshop 5.0; Adobe Systems, San Jose, CA). This procedure allowed us to make important structures,
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such as the inferior pole of the patella, more obvious. Thus, the measuring procedure with a CAD-program (Autocad Release 14.0; Autodesk, San Rafeal, CA) was made easy. The values measured were the surface area of the ultrasound cross-sections of the PT, the angle of the sulcus, the lateral patellofemoral angle, the Merchant’s congruence angle, and the height of the patella using the Caton Method17,23,27-30 (Fig 1). All of these variables were compared with those of the contralateral healthy knee. All statistical analyses were performed using the Student t test, with the significance level set at P ⫽ .05. RESULTS Over the first 30 postoperative months, the ultrasound evaluation of the PT showed a significant increase (0.33 cm2) in the surface area of 20.48% (P ⫽ .05). After the 30th postoperative month, a significant decrease (⫺0.08 cm2) of 4.88% was found (P ⫽ .0008). The ultrasound evaluation revealed healing of the defect so that 30 months postoperatively, the cross-section area of the PT reached 95.12% of the area of the contralateral healthy tendon. However, there are 2 paths to this final situation. A hypertrophy of the tendon was found in 20 patients in group A; in the remaining 7 patients in group A, the defect was visible. In patients examined after the 30th postoperative month (group B), there was a tight cluster around 95.12% of the surface area of the healthy tendon (Fig 2, Table 1). After the third month, the echogenicity of the donor defect was similar to that of the neighboring tendon tissue. The measurement of patellar height as an indicator of patella baja, carried out from the postoperative months 3 to 30, showed a mean decrease of 9.21% (P ⫽ .01) and from postoperative months 30 to 70, a mean decrease of 7.02% (P ⫽ .03) compared with the patellar height of the healthy knee joint (Table 1). In the first postoperative months, the Merchant’s congruence angle, as an indicator of medial or lateral subluxation of the patella, showed a large variation in measurements for lateral and medial patella displacement. In group A, the average value of the Merchant’s congruence angle increased by 11.59° (P ⫽ .0004) and in group B it increased only by 3.82°. This finding indicates a nonsignificant slight lateral relocation of the patella (Fig 3, Table 1). In 2 patients, the value of the Merchant’s congruence angle was close to the outer limits of normal. One month later, the radiological evaluation of these 2 patients showed all values well within normal range. A nonsignificant increase
FIGURE 1. (A) Ultrasound measurement of the cross-section of the PT. (B) Measurement of the sulcus angle (␣) and of the Merchant’s congruence angle (␣⬘). (C) Measurement of the lateral patellofemoral angle (␥). (a, the deepest point of the sulcus; b and b⬘, highest points of the femoral condyles; c, deepest point of the patella; d, lateral end of the patellar facet; e, angle that divides the sulcus angle.)
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FIGURE 2. Percentage changes in ultrasound area of the standard PT cross-sections, clearly illustrating the 2 different healing types for the harvesting defects. Type 1 (dashed line), slow healing of the defect. Type 2 (dotted line), initial hypertrophy, followed by a slow reduction of tissue mass until the final strength of the PT is reached. Very infrequently in postoperative month 4, there is a very obvious enlargement of the PT (100%). The ultrasound picture in these cases shows edema of the tendon.
(P ⫽ .23) of 1.18° was found for the lateral patellofemoral angle. A nonsignificant change of the sulcus angle was also found, which indicates the high precision of the radiographs according to Muellner et al.20 DISCUSSION This study shows that after harvesting the medial third of the PT as BPTB graft, the changes in the patella height and congruence angle in the extensor mechanism of the knee joint are similar to those after harvesting the central third.16-18,22 This can be explained by the fact that other factors rather than the harvesting itself are responsible for changes in the extensor mechanism. Any procedure around the PT, even without harvesting of a transplant, can cause contraction.8,9,17,18 Ultrasound evaluation of the cross-section area of the tendon indicates that there are 2 distinct types of healing after harvesting the medial third of the PT. In the first type, including 20 of the 27 patients in group A, the donor defect heals rapidly with scar tissue and the cross-section area of the tendon appears to be enlarged about 40% during the first postoperative period. This “hypertrophic” PT subsequently decreases in area and 2.5 years postoperatively attains its final state, which is 95% of the cross-section area of the control tendon. Our result is in agreement with find-
ings of other investigators.7-9,12,31,32 They have reported an enlargement of the tendon, which reached a peak 6 months postoperatively. Furthermore, using magnetic resonance imaging and ultrasound evaluation, they found a normal condition in the donor defect between 2 and 2.5 years postoperatively. In the second healing type, involving the remaining 7 patients in group A, the donor defect heals progressively until the cross-section area of the tendon reaches about 95% of the area of the control tendon. Nevertheless, 2.5 years postoperatively, the cross-section area decreased by 5% of the preoperative area irrespective of the type of healing process. The prolonged healing process found in our study is in agreement with the findings of other investigators who have also reported that the tendon reaches its final size 2 to 2.5 years postoperatively.8,9,12,32,33 In all of these studies, the central third of the PT was used as graft, except in the study of Nixon et al.9 in which the medial third was used. However, Rosenberg et al.15 and Kohn and Sander-Beuermann.31 reported no healing when the peritendon was not closed. The effect of the rehabilitation program on the healing process of the tendon has been investigated using animal models. As has been proposed by Cabaud et al.,21 the immobilization of the operated knee in a cast, after harvesting the medial third of the PT, results in hypertrophy only at the under surface and partial healing of the tendon. In contrast, Burks et al.10 and Linder et al.22 reported that the immediate use of the knee and the unrestricted activity of the animals are associated with scar formation of the entire tendon’s defect after harvesting either the medial or the central third of the tendon. They hypothe-
FIGURE 3. Measurement of the Merchant’s congruence angle. There is a large variation during the first postoperative months. Step-wise stabilization of the value. Thirty months postoperatively, the values are close to baseline values.
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TABLE 1. Results of Evaluation of Ultrasound Images and Radiographs Operated Knee Mean ⫾ SD (range) Area of PT slices 1-30 mo 1.99 ⫾ 0.20 cm2 (1.66-2.10) 30-70 mo 1.57 ⫾ 0.19 cm2 (1.41-1.82) Congruence angle 1-30 mo 6.24 ⫾ 7.50° (⫺8.58-16.16) 30-70 mo ⫺1.03 ⫾ 1.88° (⫺4.38-6.45) Lateral patellofemoral angle 1-30 mo 18.08 ⫾ 4.12° (16.92-20.14) 30-70 mo 18.71 ⫾ 4.68° (15.71-20.38) Patellar height 1-30 mo 32.8 ⫾ 4.42 mm (26.91-36.34) 30-70 mo 32.2 ⫾ 4.95 mm (28.12-35.58) Sulcus angle 142.1 ⫾ 5.72° (129.2-146.5)
sized that early joint mobility produces stresses in the remaining tendon, leading to microdamage and repair processes that involve the entire tendon. Furthermore, according to Sanchis-Alfonso et al.,11 a postoperative rehabilitation protocol that allows aggressive mobilization is not restricted because they found that scar tissue was present only in the central third of the tendon (donor-site defect). In all of our patients, the operated knee was mobilized early, although the intensity with which the rehabilitation program was followed varied among patients. This can possibly explain the different healing pathways. Also, grafting of the harvesting defect of the bone blocks has perhaps influenced the healing of the tendon defect in all of our patients. This hypothesis is supported by other investigators.10,14,31 However, further investigation is needed to clarify the importance of the rehabilitation protocols on the healing process of the donor-site defect. After harvesting the BPTB graft, the patella position can change. There is a relocation of the patella medially or laterally affecting the Merchant’s congruence angle. The patella can be rotated, affecting the lateral patellofemoral angle, and finally it can be displaced proximally or distally as a result of PT shortening or lengthening. In our study, the lateral patellofemoral angle did not undergo any changes. No other studies have documented changes of the patella tilt after harvesting of a BPTB graft. During the first postoperative period, there is a large variation of the Merchant’s angle. In group A, there was a mean average patellar displacement of 11.59°. From postoperative month 6, the variation of the Merchant’s congruence angle begins to decrease and reaches the final value of 3.82° 30 months postoper-
Contralateral Knee Mean ⫾ SD (range)
Change
Change
P Value
1.66 ⫾ 0.14 cm2 (1.37-1.96) 1.65 ⫾ 0.18 cm2 (1.39-1.84)
0.33 cm2 ⫺0.08 cm2
20.48% ⫺4.88%
.05 .0008
⫺5.35 ⫾ 5.06° ⫺4.85 ⫾ 6.78°
(⫺8.76-9.93) (⫺7.43-4.65)
11.59° 3.82°
16.97 ⫾ 4.52° 17.42 ⫾ 4.21°
(13.98-20.10) (16.17-19.72)
1.11° 1.30°
36.1 ⫾ 3.93 mm (33.33-37.87) 34.6 ⫾ 4.63 mm (29.32-37.19) 142.6° ⫾ 5.99 (128.3-147.1)
⫺3.32 mm ⫺2.43 mm ⫺0.5°
.0004 .38 6.54% 7.45%
.18 .15
9.21% 7.02% ⫺0.39%
.01 .03 .26
atively. This indicates a minor and nonsignificant lateral patellar displacement. The minor displacement observed may be related to the operating technique. According to Hertel’s procedure,26 the harvesting of the medial third of the tendon is performed without damage to the attachment of the medial patellofemoral ligament, the patellomeniscal ligament, or the medial retinacular fibers. This provides 75%34 of the restraining forces that prevent lateral displacement of the patella. The initial postoperative variations, followed by a progressive decrease in the Merchant’s congruence angle, can be explained by consolidation of the defect’s scar tissue, which leads to a balance between the lateral and medial tension. Another possible explanation is the restoration of the muscle strength in the vastus medialis as a dynamic stabilizator. However, this hypothesis requires further investigation. Moreover, it has been proposed that the harvesting of the central third of the PT does not affect the Merchant’s congruence angle, although Muellner et al.20 have reported a slight medial patella migration of 5°. In addition, Breitfuss et al.35 found signs of medial patellofemoral arthritis in 25% of their patients on plain radiographs because of patella position changes. Explanations given were that either the harvesting was not exactly centrally located, or that scarring is not limited to the graft harvesting site.17,35 Another complication that has been reported is the shortening of the PT after harvesting of a BPTB graft. In our study, the shortening of the PT was 9.21% during the early postoperative period (group A), whereas the final shortening was 7.02% (group B). Both results are similar to length changes reported by Muellner et al.17 and Linder et al.22 in human and animal studies, respectively. They found that slight
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improvement in length occurred with time. The reported decrease of the patella height, after harvesting the medial third of the PT, is about 10%.10,16,18,31,35 Shaffer et al.18 found in 13 of 36 patients a lower incidence of tendon shortening (less than 4%). They suggested that, technically, the measurement error for detection of tendon length changes varied from 5.5% to 15%, depending on the measurement technique. The technique used in our study for measurement of the distance between the lower patellar bone and the intra-articular tibial level has a measurement error of 10%.9 No significant shortening was reported by Cerullo et al.36 in their study. In addition, the immobilization of the operated knee postoperatively is related to a higher incidence of shortening.37 CONCLUSIONS The results of our study indicate that harvesting of the medial third of the PT as BPTB graft does not result in patellar rotation because there was no influence on the patellofemoral angle. The use of the medial third of the PT is associated with a nonsignificant lateral patellar displacement; however, there is a slight medial patellar displacement after using the central third. In addition, the PT shortening is similar to that occurring after using the central third and is within the limits of technical error. Finally, the tendon defect always heals and the cross-section area of the tendon reaches 95% that of the contralateral tendon after postoperative month 30. However, there are 2 types of tendon defect healing, either immediate healing associated with hypertrophy or progressive healing.
8.
9. 10. 11.
12. 13. 14.
15.
16. 17.
18. 19.
20.
REFERENCES 21. 1. Noyes FR, Butler DI, Paulos LE, et al. Biomechanical analysis of human ligament grafts used in knee-ligament repairs and reconstruction. J Bone Joint Surg Am 1983;66:344-352. 2. Clancy WG, Nelson DA, Reider B, Narechania RG. Anterior cruciate ligament reconstruction using one-third of the patellar ligament, augmented by extra-articular tendon transfers. J Bone Joint Surg Am 1982;64:353-359. 3. Arnoczky SP, Tarvin GB, Marshall JL. Anterior cruciate ligament replacement using patellar tendon. J Bone Joint Surg Am 1982;64:217-224. 4. Hughston JC. Complications of anterior cruciate ligament surgery. Orthop Clin North Am 1985;16:237-240. 5. Paulos LO, Wnorowski DC, Greenwald AE. Intrapatellar contracture syndrome. Am J Sports Med 1994;22:440-449. 6. Sachs RA, Daniel DM, Stone ML, Garfein RF. Patellofemoral problems after anterior cruciate ligament reconstruction. Am J Sports Med 1989;17:760-765. 7. Coupens SD, Yates CT, Sheldon C, Ward C. Magnetic resonance imaging evaluation of the patellar tendon after use of its
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central one-third for anterior cruciate ligament reconstruction. Am J Sports Med 1992;20:332-335. Meisterling RC, Wadsworth T, Ardill R, Griffiths H, LaneLarsen CL. Morphologic changes in the human patellar tendon after bone-tendon-bone anterior cruciate ligament reconstruction. Clin Orthop Rel Res 1993;289:208-212. Nixon RG, SeGall GK, Sax SL, Cain TE, Tullos HS. Reconstruction of the patellar tendon donor site after graft harvest. Clin Orthop 1995;317:162-171. Burks RT, Haut RC, Lancester RL. Biomechanical and histological observations of the dog patellar tendon after removal of its central one-third. Am J Sports Med 1990;18:146-153. Sanchis-Alfonso V, Subias Lopez A, Monteagudo-Castro C, Rosello-Sastre E. Healing of the patellar tendon donor defect created after central third patellar tendon harvest. Knee Surg Sports Traumatol Arthrosc 1999;7:340-348. Proctor CS, Jackson DW, Simon TM. Characterisation of the repair tissue after removal of the central one-third of the patellar ligament. J Bone Joint Surg Am 1997;97:997-1006. Karns DJ, Heidt RS, Holladay BR, Colosimo AJ. Case report: Revision anterior cruciate ligament reconstruction. Arthroscopy 1994;10:148-151. Adriani E, Marianu PP, Maresca G, Santori N. Healing of the patellar tendon after harvesting of its mid-third for anterior cruciate ligament reconstruction and evolution of the unclosed donor side defect. Knee Surg Sports Traumatol Arthrosc 1995; 3:138-143. Rosenberg TD, Franklin JL, Baldwin GN, Nelson KA. Extensor mechanism function after patellar tendon graft harvest for anterior cruciate ligament reconstruction. Am J Sports Med 1992;20:519-526. Dandy D, Desai SS. Patellar tendon length after anterior cruciate ligament reconstruction. J Bone Joint Surg Br 1994;76: 198-199. Muellner T, Kaltenbrunner W, Nicolic A, Mittelboeck M, Schabus R, Vescei V. Shortening of the patellar tendon after anterior cruciate ligament reconstruction. Arthroscopy 1998; 14:592-596. Shaffer BS, Tibone JE. Patellar tendon length change after anterior cruciate ligament reconstruction using the midthird patellar tendon. Am J Sports Med 1993;21:449-454. Shino K, Nakagawa S, Inoue M, Horibe S, Yoneda M. Deterioration of the patellofemoral articular surfaces after anterior cruciate ligament reconstruction. Am J Sports Med 1993;21: 206-211. Muellner T, Kaltenbrunner W, Nicolic A, Mittelboeck M, Schabus R, Vescei V. Anterior cruciate ligament reconstruction alters the patellar alignment. Arthroscopy 1999;15:165168. Cabaud HE, Feagin JA, Rodkey WG. Acute anterior cruciate ligament injury and augmented repair. Am J Sports Med 1980; 8:395-401. Linder LH, Sukin DL, Burks RT, Haut RC. Biomechanical and histological properties of the canine patellar tendon after removal of its medial third. Am J Sports Med 1994;22:136-142. Merchant AC, Mercer RL, Jacobsen RH, Cool CR. Roentgenographic analysis of patellofemoral congruence. J Bone Joint Surg Am 1974;56:1391-1396. Georgoulis AD, Papageorgiou CD, Makris CA, Moebius UG, Soucacos PN. Anterior cruciate ligament reconstruction with the press-fit technique: 2.5 years follow up of 42 patients. Acta Orthop Scand Suppl 1997;275:42-45. Hertel P, Bernard M. Vordere Kreuzbandersatzplastik— Vorteile einer metallfreien offenen Press-Fit Operationstechnik (Einschmittechnik) gegenuber einer arthroskopischen Unitunnel-Technik In: Kohn D, Wirth CJ, eds. Arthroskopische versus offene Operationen. Stuttgart: Ferdinand Enke Verlag, 1994. Lais E. Eine primaer uebungsstabile autologe Vordere Kreuz-
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bandplastik (Implantationstechnik, biomechanische Grundlagen, klinische Anwendung und Ergebnisse). Habilitation Freie Universitat Berlin, July 1991. Aglietti P, Insall JN, Cerulli G. Patella pain and incongruence. Clin Orthop Rel Res 1983;176:217-224. Jensen CM, Rosen JU. Acute traumatic dislocations of the patella. J Trauma 1985;25:1601-1062. Laurin CA, Dussault R, Levesque HP. The tangential investigation of the patellofemoral joint. Clin Orthop Rel Res 1979; 144:16-26. Berg EE, Mason SL, Michael J. Patellar height ratios. Am J Sports Med 1996;24:218-221. Kohn D, Sander-Beuermann A. Donor-site morbidity after harvest of a bone-tendon-bone patellar tendon graft. Knee Surg Sports Traumatol Arthrosc 1994;2:219-223. Brandsson S, Faxen E, Eriksson BI, Kalebo P, Sward L, Lundin O, Karlsson J. Closing patellar tendon defects after anterior cruciate ligament reconstruction: Absence of any benefit. Knee Surg Sports Traumatol Arthrosc 1998;6:82-87.
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33. Frank C, Amiel MS, Woo SL, Akeson W. Normal ligament properties and ligament healing. J Orthop Res 1985;1:179188. 34. Boden B, Pearsall A, Garret W, Feagin J. Patellofemoral instability: Evaluation and management. J Am Acad Orthop Surg 1997;5:47-57. 35. Breitfuss H, Frohlich R, Povacz P, Resch H, Wicker A. The tendon defect after anterior cruciate ligament reconstruction using the midthird patellar tendon—A problem for the patellofemoral joint? Knee Surg Sports Traumatol Arthrosc 1996; 3:194-198. 36. Cerullo G, Puddu G, Gianni E, Damiani A, Pigozzi F. Anterior cruciate ligament patella tendon reconstruction: It is probably better to leave the tendon defect open! Knee Surg Sports Traumatol Arthrosc 1995;3:14-17. 37. O’Brien SJ, Warren RF, Pavlov H, Panariello R, Wickiewicz TL. Reconstruction of the chronically insufficient anterior cruciate ligament with the central third of the patellar ligament. J Bone Joint Surg Am 1991;73:278-286.
Purpose: The objective of this study was the ultrasound evaluation of the donor defect of the patellar tendon (PT) and the radiologic evaluation of the patella after harvesting of the medial third as a bone–patella tendon– bone (BPTB) graft for anterior cruciate ligament (ACL) reconstruction. Type of Study: This was a cohort study. Methods: In 45 patients who had ACL reconstruction, the extensor apparatus of the donor side was studied using ultrasound cross-sections and radiographs (anteroposterior, lateral, and a tangential view of the patella) 3 to 70 months postoperatively. Patients were divided into two groups. The early postoperative group (3 to 30 months postoperative) consisted of 27 patients (group A) and the late postoperative group (31 to 70 months postoperative) consisted of 18 patients (group B). The healthy contralateral extensor apparatus was used as control. Results: In group A, the standard ultrasound cross-section area of the PT increased by 20.48%, whereas in group B, it decreased by 4.88%. In group A, the patellar height was decreased by 9.21% in the donor side compared with the control. In group B, the patellar height was decreased by 7.02%. In group A, the Merchant’s congruence angle increased by 11.59°, and for group B, this angle increased by 3.82°. This finding indicated that, after the 30th postoperative month, lateral displacement of the patella was not statistically significant (P ⫽ .38). In addition, no significant differences were found in the lateral patellofemoral angle in either group. Conclusions: Our study indicates that the tendon defect is always healed and the final tendon cross-section area is 95% of the contralateral after the 30th postoperative month. In addition, there was a nonsignificant slight lateral displacement of the patella. In contrast, other studies found shown that there is a slight medial displacement of the PT after using the central third as a BPTB graft. Key Words: Anterior cruciate ligament—Medial third BPTB graft—Patellar alignment—Harvesting defect healing—Ultrasound evaluation.
A
s a bone–patellar tendon– bone (BPTB) graft for anterior cruciate ligament (ACL) reconstruction, one third of the patellar tendon (PT) is widely used because of the biomechanical characteristics of the graft and the stable fixation of the bone plugs that allow early mobilization.1-3 This technique has many
From the Department of Orthopaedic Surgery, Medical School, University of Ioannina, Ioannina, Greece. Address correspondence and reprint requests to Anastasios D. Georgoulis, M.D., Department of Orthopaedic Surgery, Medical School of Ioannina, PO Box 1042, Ioannina 45 110, Greece. E-mail: [email protected] © 2001 by the Arthroscopy Association of North America 0749-8063/01/1709-2583$35.00/0 doi:10.1053/jars.2001.25957
advantages including graft strength similar to the original ACL ligament, but there are disadvantages that can reduce successful patient outcome. Some of these disadvantages are complications and problems related to the donor-site defect and its healing process. Complications include patella fracture, PT avulsion, lateral or medial subluxation of the patella, and patella baja.4-6 The healing process of the donor defect has been studied mainly after BPTB harvesting of the central third of the PT. Some investigators, using ultrasound and magnetic resonance imaging, have reported hypertrophy of the PT postoperatively and healing of the donor defect with scar tissue.7-9 Indeed, in animal studies, the donor defect is replaced with scar tissue
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that does not assume the histologic and biomechanical properties of the neighboring tendon tissue.10-12 Furthermore, Nixon et al.9 found scar tissue in a biopsy specimen from the donor site of the PT that was nearly identical to normal tendon tissue. Karns et al.,13 using the donor defect tissue in revision ACL surgery, also found a normal histologic picture 4 years after primary ACL reconstruction. However, other investigators have reported partial or no healing of the defect 2 years postoperatively.14,15 Possibly, the different reported results are related to the closing or not of the peritendon in the donor site.12 Another question remaining is whether harvesting of the BPTB graft alters the patella position in the femoral trochlea, causing either patella baja, or sideways displacement. Many authors refer to the harvesting procedure as the cause of shrinkage of the PT or as a partial cause of infrapatellar contracture syndrome.5,16-18 Arthroscopically detected changes of the patellofemoral joint have been reported as a result of alteration to the extensor mechanism after PT harvesting.19 In a study examining the alignment of the patella after harvesting of the central third of the PT,20 a change in the Merchant’s angle of about 4.7° was found in a 2-year follow-up period. This finding indicated that, while the lateral patellofemoral angle remains the same, medial relocation of the patella occurs. Most studies of the extensor mechanism are focused on the alterations after harvesting the central third of the PT. There have been only a few reports on changes of the extensor mechanism after use of the medial third of the PT.16,21,22 The purpose of our study was the ultrasound examination of the PT donor defect and the radiologic investigation of the patella after harvesting of the medial third as BPTB graft for ACL reconstruction. METHODS Forty-five patients (34 men and 11 women; mean age, 26.1 years) who had undergone ACL reconstruction using the medial third of the PT were re-examined 3 months to 6 years postoperatively (mean interval, 26.6 months). Patients with procedures to the contralateral knee joint or any lesion of the extensor mechanism were excluded from this cohort study. In a preliminary study, large variations were found during the first 30 postoperative months. After the 30th postoperative month, the Merchant’s congruence angle23 and ultrasound cross-section area remained unchanged. Thus, in our study the patients were di-
vided into 2 groups; 27 patients (group A) were examined 3 to 30 months postoperatively (mean interval, 10.3 months) and 18 patients (group B) were examined 31 to 70 months postoperatively (mean interval, 49.2 months). In all patients, ACL reconstruction was performed using the press-fit technique as described by Hertel et al.24-26 According to this technique, the medial third of the patella is used as a graft because of the flag-like shape of the bone block harvested from the patella. The peritenon was carefully sutured after the harvesting procedure. Furthermore, the bone defects of the patella and the tibia were always filled either by autograft or allograft. The postoperative rehabilitation program was as follows. Isometric training of the thigh muscles was started on the first postoperative day; movement of the knee joint was permitted from 0° to 90° of flexion during the first 2 weeks; walking with the aid of crutches and using an extension brace for 4 weeks; after postoperative week 4, step-wise weight bearing was commenced, and by postoperative week 6, full weight bearing was allowed. After 2 months, jogging was permitted. Before participation in sporting activities, proprioception training was carried out. The PT was examined using a standard ultrasound device with a 7.5-MHz high-resolution linear transducer. The knee joint was flexed at 90° to ensure adequate tension of the tendon. The tibial tuberosity was palpated, and the lower edge of the transducer was attached to the upper edge of the tuberosity. Using this protocol, a standard sagittal cross-section, 0.5 cm above the upper edge of the tuberositas tibiae, was taken and measured. The images were developed on film. To ensure that the PT of the contralateral knee could be used as control, we examined the PT of 15 volunteers with intact knee joints. No significant differences were found between the right and the left PT crosssection area in the volunteers. The width and thickness of the PT could not be accurately measured because these parameters are affected during examination by pressure of the ultrasound transducer on the tendon. The patients’ knees were also evaluated using lateral radiographs of the knee joint at 30° of flexion and tangential radiographs of the patella. The ultrasound images were digitized so as to reduce the examination time and leave the ultrasound system free for hospital use. Radiographs were also digitized and then processed using an image-processing program (Adobe Photoshop 5.0; Adobe Systems, San Jose, CA). This procedure allowed us to make important structures,
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such as the inferior pole of the patella, more obvious. Thus, the measuring procedure with a CAD-program (Autocad Release 14.0; Autodesk, San Rafeal, CA) was made easy. The values measured were the surface area of the ultrasound cross-sections of the PT, the angle of the sulcus, the lateral patellofemoral angle, the Merchant’s congruence angle, and the height of the patella using the Caton Method17,23,27-30 (Fig 1). All of these variables were compared with those of the contralateral healthy knee. All statistical analyses were performed using the Student t test, with the significance level set at P ⫽ .05. RESULTS Over the first 30 postoperative months, the ultrasound evaluation of the PT showed a significant increase (0.33 cm2) in the surface area of 20.48% (P ⫽ .05). After the 30th postoperative month, a significant decrease (⫺0.08 cm2) of 4.88% was found (P ⫽ .0008). The ultrasound evaluation revealed healing of the defect so that 30 months postoperatively, the cross-section area of the PT reached 95.12% of the area of the contralateral healthy tendon. However, there are 2 paths to this final situation. A hypertrophy of the tendon was found in 20 patients in group A; in the remaining 7 patients in group A, the defect was visible. In patients examined after the 30th postoperative month (group B), there was a tight cluster around 95.12% of the surface area of the healthy tendon (Fig 2, Table 1). After the third month, the echogenicity of the donor defect was similar to that of the neighboring tendon tissue. The measurement of patellar height as an indicator of patella baja, carried out from the postoperative months 3 to 30, showed a mean decrease of 9.21% (P ⫽ .01) and from postoperative months 30 to 70, a mean decrease of 7.02% (P ⫽ .03) compared with the patellar height of the healthy knee joint (Table 1). In the first postoperative months, the Merchant’s congruence angle, as an indicator of medial or lateral subluxation of the patella, showed a large variation in measurements for lateral and medial patella displacement. In group A, the average value of the Merchant’s congruence angle increased by 11.59° (P ⫽ .0004) and in group B it increased only by 3.82°. This finding indicates a nonsignificant slight lateral relocation of the patella (Fig 3, Table 1). In 2 patients, the value of the Merchant’s congruence angle was close to the outer limits of normal. One month later, the radiological evaluation of these 2 patients showed all values well within normal range. A nonsignificant increase
FIGURE 1. (A) Ultrasound measurement of the cross-section of the PT. (B) Measurement of the sulcus angle (␣) and of the Merchant’s congruence angle (␣⬘). (C) Measurement of the lateral patellofemoral angle (␥). (a, the deepest point of the sulcus; b and b⬘, highest points of the femoral condyles; c, deepest point of the patella; d, lateral end of the patellar facet; e, angle that divides the sulcus angle.)
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FIGURE 2. Percentage changes in ultrasound area of the standard PT cross-sections, clearly illustrating the 2 different healing types for the harvesting defects. Type 1 (dashed line), slow healing of the defect. Type 2 (dotted line), initial hypertrophy, followed by a slow reduction of tissue mass until the final strength of the PT is reached. Very infrequently in postoperative month 4, there is a very obvious enlargement of the PT (100%). The ultrasound picture in these cases shows edema of the tendon.
(P ⫽ .23) of 1.18° was found for the lateral patellofemoral angle. A nonsignificant change of the sulcus angle was also found, which indicates the high precision of the radiographs according to Muellner et al.20 DISCUSSION This study shows that after harvesting the medial third of the PT as BPTB graft, the changes in the patella height and congruence angle in the extensor mechanism of the knee joint are similar to those after harvesting the central third.16-18,22 This can be explained by the fact that other factors rather than the harvesting itself are responsible for changes in the extensor mechanism. Any procedure around the PT, even without harvesting of a transplant, can cause contraction.8,9,17,18 Ultrasound evaluation of the cross-section area of the tendon indicates that there are 2 distinct types of healing after harvesting the medial third of the PT. In the first type, including 20 of the 27 patients in group A, the donor defect heals rapidly with scar tissue and the cross-section area of the tendon appears to be enlarged about 40% during the first postoperative period. This “hypertrophic” PT subsequently decreases in area and 2.5 years postoperatively attains its final state, which is 95% of the cross-section area of the control tendon. Our result is in agreement with find-
ings of other investigators.7-9,12,31,32 They have reported an enlargement of the tendon, which reached a peak 6 months postoperatively. Furthermore, using magnetic resonance imaging and ultrasound evaluation, they found a normal condition in the donor defect between 2 and 2.5 years postoperatively. In the second healing type, involving the remaining 7 patients in group A, the donor defect heals progressively until the cross-section area of the tendon reaches about 95% of the area of the control tendon. Nevertheless, 2.5 years postoperatively, the cross-section area decreased by 5% of the preoperative area irrespective of the type of healing process. The prolonged healing process found in our study is in agreement with the findings of other investigators who have also reported that the tendon reaches its final size 2 to 2.5 years postoperatively.8,9,12,32,33 In all of these studies, the central third of the PT was used as graft, except in the study of Nixon et al.9 in which the medial third was used. However, Rosenberg et al.15 and Kohn and Sander-Beuermann.31 reported no healing when the peritendon was not closed. The effect of the rehabilitation program on the healing process of the tendon has been investigated using animal models. As has been proposed by Cabaud et al.,21 the immobilization of the operated knee in a cast, after harvesting the medial third of the PT, results in hypertrophy only at the under surface and partial healing of the tendon. In contrast, Burks et al.10 and Linder et al.22 reported that the immediate use of the knee and the unrestricted activity of the animals are associated with scar formation of the entire tendon’s defect after harvesting either the medial or the central third of the tendon. They hypothe-
FIGURE 3. Measurement of the Merchant’s congruence angle. There is a large variation during the first postoperative months. Step-wise stabilization of the value. Thirty months postoperatively, the values are close to baseline values.
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TABLE 1. Results of Evaluation of Ultrasound Images and Radiographs Operated Knee Mean ⫾ SD (range) Area of PT slices 1-30 mo 1.99 ⫾ 0.20 cm2 (1.66-2.10) 30-70 mo 1.57 ⫾ 0.19 cm2 (1.41-1.82) Congruence angle 1-30 mo 6.24 ⫾ 7.50° (⫺8.58-16.16) 30-70 mo ⫺1.03 ⫾ 1.88° (⫺4.38-6.45) Lateral patellofemoral angle 1-30 mo 18.08 ⫾ 4.12° (16.92-20.14) 30-70 mo 18.71 ⫾ 4.68° (15.71-20.38) Patellar height 1-30 mo 32.8 ⫾ 4.42 mm (26.91-36.34) 30-70 mo 32.2 ⫾ 4.95 mm (28.12-35.58) Sulcus angle 142.1 ⫾ 5.72° (129.2-146.5)
sized that early joint mobility produces stresses in the remaining tendon, leading to microdamage and repair processes that involve the entire tendon. Furthermore, according to Sanchis-Alfonso et al.,11 a postoperative rehabilitation protocol that allows aggressive mobilization is not restricted because they found that scar tissue was present only in the central third of the tendon (donor-site defect). In all of our patients, the operated knee was mobilized early, although the intensity with which the rehabilitation program was followed varied among patients. This can possibly explain the different healing pathways. Also, grafting of the harvesting defect of the bone blocks has perhaps influenced the healing of the tendon defect in all of our patients. This hypothesis is supported by other investigators.10,14,31 However, further investigation is needed to clarify the importance of the rehabilitation protocols on the healing process of the donor-site defect. After harvesting the BPTB graft, the patella position can change. There is a relocation of the patella medially or laterally affecting the Merchant’s congruence angle. The patella can be rotated, affecting the lateral patellofemoral angle, and finally it can be displaced proximally or distally as a result of PT shortening or lengthening. In our study, the lateral patellofemoral angle did not undergo any changes. No other studies have documented changes of the patella tilt after harvesting of a BPTB graft. During the first postoperative period, there is a large variation of the Merchant’s angle. In group A, there was a mean average patellar displacement of 11.59°. From postoperative month 6, the variation of the Merchant’s congruence angle begins to decrease and reaches the final value of 3.82° 30 months postoper-
Contralateral Knee Mean ⫾ SD (range)
Change
Change
P Value
1.66 ⫾ 0.14 cm2 (1.37-1.96) 1.65 ⫾ 0.18 cm2 (1.39-1.84)
0.33 cm2 ⫺0.08 cm2
20.48% ⫺4.88%
.05 .0008
⫺5.35 ⫾ 5.06° ⫺4.85 ⫾ 6.78°
(⫺8.76-9.93) (⫺7.43-4.65)
11.59° 3.82°
16.97 ⫾ 4.52° 17.42 ⫾ 4.21°
(13.98-20.10) (16.17-19.72)
1.11° 1.30°
36.1 ⫾ 3.93 mm (33.33-37.87) 34.6 ⫾ 4.63 mm (29.32-37.19) 142.6° ⫾ 5.99 (128.3-147.1)
⫺3.32 mm ⫺2.43 mm ⫺0.5°
.0004 .38 6.54% 7.45%
.18 .15
9.21% 7.02% ⫺0.39%
.01 .03 .26
atively. This indicates a minor and nonsignificant lateral patellar displacement. The minor displacement observed may be related to the operating technique. According to Hertel’s procedure,26 the harvesting of the medial third of the tendon is performed without damage to the attachment of the medial patellofemoral ligament, the patellomeniscal ligament, or the medial retinacular fibers. This provides 75%34 of the restraining forces that prevent lateral displacement of the patella. The initial postoperative variations, followed by a progressive decrease in the Merchant’s congruence angle, can be explained by consolidation of the defect’s scar tissue, which leads to a balance between the lateral and medial tension. Another possible explanation is the restoration of the muscle strength in the vastus medialis as a dynamic stabilizator. However, this hypothesis requires further investigation. Moreover, it has been proposed that the harvesting of the central third of the PT does not affect the Merchant’s congruence angle, although Muellner et al.20 have reported a slight medial patella migration of 5°. In addition, Breitfuss et al.35 found signs of medial patellofemoral arthritis in 25% of their patients on plain radiographs because of patella position changes. Explanations given were that either the harvesting was not exactly centrally located, or that scarring is not limited to the graft harvesting site.17,35 Another complication that has been reported is the shortening of the PT after harvesting of a BPTB graft. In our study, the shortening of the PT was 9.21% during the early postoperative period (group A), whereas the final shortening was 7.02% (group B). Both results are similar to length changes reported by Muellner et al.17 and Linder et al.22 in human and animal studies, respectively. They found that slight
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improvement in length occurred with time. The reported decrease of the patella height, after harvesting the medial third of the PT, is about 10%.10,16,18,31,35 Shaffer et al.18 found in 13 of 36 patients a lower incidence of tendon shortening (less than 4%). They suggested that, technically, the measurement error for detection of tendon length changes varied from 5.5% to 15%, depending on the measurement technique. The technique used in our study for measurement of the distance between the lower patellar bone and the intra-articular tibial level has a measurement error of 10%.9 No significant shortening was reported by Cerullo et al.36 in their study. In addition, the immobilization of the operated knee postoperatively is related to a higher incidence of shortening.37 CONCLUSIONS The results of our study indicate that harvesting of the medial third of the PT as BPTB graft does not result in patellar rotation because there was no influence on the patellofemoral angle. The use of the medial third of the PT is associated with a nonsignificant lateral patellar displacement; however, there is a slight medial patellar displacement after using the central third. In addition, the PT shortening is similar to that occurring after using the central third and is within the limits of technical error. Finally, the tendon defect always heals and the cross-section area of the tendon reaches 95% that of the contralateral tendon after postoperative month 30. However, there are 2 types of tendon defect healing, either immediate healing associated with hypertrophy or progressive healing.
8.
9. 10. 11.
12. 13. 14.
15.
16. 17.
18. 19.
20.
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bandplastik (Implantationstechnik, biomechanische Grundlagen, klinische Anwendung und Ergebnisse). Habilitation Freie Universitat Berlin, July 1991. Aglietti P, Insall JN, Cerulli G. Patella pain and incongruence. Clin Orthop Rel Res 1983;176:217-224. Jensen CM, Rosen JU. Acute traumatic dislocations of the patella. J Trauma 1985;25:1601-1062. Laurin CA, Dussault R, Levesque HP. The tangential investigation of the patellofemoral joint. Clin Orthop Rel Res 1979; 144:16-26. Berg EE, Mason SL, Michael J. Patellar height ratios. Am J Sports Med 1996;24:218-221. Kohn D, Sander-Beuermann A. Donor-site morbidity after harvest of a bone-tendon-bone patellar tendon graft. Knee Surg Sports Traumatol Arthrosc 1994;2:219-223. Brandsson S, Faxen E, Eriksson BI, Kalebo P, Sward L, Lundin O, Karlsson J. Closing patellar tendon defects after anterior cruciate ligament reconstruction: Absence of any benefit. Knee Surg Sports Traumatol Arthrosc 1998;6:82-87.
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33. Frank C, Amiel MS, Woo SL, Akeson W. Normal ligament properties and ligament healing. J Orthop Res 1985;1:179188. 34. Boden B, Pearsall A, Garret W, Feagin J. Patellofemoral instability: Evaluation and management. J Am Acad Orthop Surg 1997;5:47-57. 35. Breitfuss H, Frohlich R, Povacz P, Resch H, Wicker A. The tendon defect after anterior cruciate ligament reconstruction using the midthird patellar tendon—A problem for the patellofemoral joint? Knee Surg Sports Traumatol Arthrosc 1996; 3:194-198. 36. Cerullo G, Puddu G, Gianni E, Damiani A, Pigozzi F. Anterior cruciate ligament patella tendon reconstruction: It is probably better to leave the tendon defect open! Knee Surg Sports Traumatol Arthrosc 1995;3:14-17. 37. O’Brien SJ, Warren RF, Pavlov H, Panariello R, Wickiewicz TL. Reconstruction of the chronically insufficient anterior cruciate ligament with the central third of the patellar ligament. J Bone Joint Surg Am 1991;73:278-286.