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Assessing arthroscopic notchplasty
Arthroscopy: The Journal of Arthroscopic and Related Surgery 1(3):2X-271 Published by Raven Press, Ltd. 0 1991 Arthroscopy Association of North America
Assessing Arthroscopic
Notchplasty
Eugene E. Berg, M.D. ~_
.~_.
Summary: To evaluate the ability to perform a widening arthroscopic
intercondylar notchplasty as part of an anterior cruciate ligament reconstruction, 20 patients had notch-width index measurements compared with either preoperative or normal-side values. The notch-width index increased an average of 0.062, correlating with absolute notch widening of 4-6 mm. This study provides
in vivo evidence that notchplasty widening can be reproducibly performed arthroscopically. The optimal notch width for reconstructive anterior cruciate ligament surgery has yet to be determined. Key Words: Notchplasty-Anterior cruciate ligament-Notch width.
reconstruction. There were 14 male and 6 female patients, whose age averaged 26% years at the time of surgery (range 17-35 years). Twelve reconstructions were performed for chronic instability, and eight were done acutely within 3 weeks of injury. Half of the patients (10) sustained noncontact injuries. Nine patients had had 12 previous procedures, none of which had included a notchplasty. All tunnel radiographic views were made with patients prone, in the 50” knee flexion, CampCoventry position (9). Six patients had preoperative tunnel views of the affected knee and these radiographs were used preferentially for comparison. The remaining patients had bilateral tunnel views obtained at maximum follow-up in which the operative knee was compared with the uninvolved side. Postoperative follow-up ranged from 6 months to 21/2 years and averaged 17 months. All patients underwent a free autogenous patellar tendon, ACL reconstruction under arthroscopic control. The notchplasty was performed with 5.5 mm-diameter spherical abrasion burr. A notchplasty of at least one burr diameter was made from the anterior aspect of the lateral intercondylar notch at its articular cartilage margin and was continued posteriorly to the condylar dropoff point. Notch-width index measurements similar to that described by Anderson and Souryal et al. were used to determine the extent of the arthroscopic inter-
The relationship of the anterior cruciate ligament (ACL) to the intercondylar notch has a significant bearing on the pathomechanics of ACL injury and its reconstruction (l-8). Norwood and Cross were the first to note that the ACL contacts the intercondylar notch when the knee is in hyperextension (6). This mechanism concentrates stress in the middle one-third of the ligament and is a cause of interstitial failure. Independent studies by Anderson and Souryal, with strong statistical correlations, confirmed that bilateral ACL ruptures occur in individuals with stenotic intercondylar notches (1,7). Thus, a wide notchplasty to prevent abrasive graft attrition has become a critical element of ACL reconstructive surgery (2,4,8). This study was undertaken to document whether a widening notchplasty can be effected reproducibly by arthroscopic methods. MATERIALS AND METHODS Bilateral tunnel knee radiographs were obtained in 20 patients who had unilateral, arthroscopic ACL From the Department of Orthopaedics, U.S.C. School of Medicine, Columbia, South Carolina, U.S.A. Address correspondence and reprint requests to Dr. E. E. Berg at Department of Orthopaedics, U.S.C. School of Medicine, Two Richland Medical Park, Suite 404, Columbia, SC 29203, U.S.A.
275
276
E. E. BERG
condylar notchplasty (1,7). The notch-width index is a ratio of measured intercondylar notch width in its middle one-third, to the width of both femoral condyles at the level of the popliteal groove on tunnel-view radiographs (7) (Fig. 1). The measurement is expressed as a ratio to minimize differences in radiographic magnification and technique. RESULTS Preoperative or normative side notch-width indices ranged from 0.158 to 0.284 and averaged 0.218. Four notch-width indices (20%) measured less than 0.200, and 10 measured less than 0.220. The postoperative notch-width index ranged from 0.225 to 0.326 and averaged 0.280. Thus, the mean index improved from a preoperative value of 0.218 to 0.280 postoperatively, increasing 0.062. The increase in notch-width index ranged from 0.032 to 0.119. If raw measurements were reduced by a 20% radiographic magnification factor, the mean index improvement of 0.062 correlates with actual notch widening of between 4 and 6 mm. Postoperatively, 17 patients had a notch-width index greater than 0.250, and only three were less than this amount. Interestingly, the patient with the narrowest nor-
mative notch-width index of 0.158 incurred a contralateral, noncontact ACL injury 7 months after the index procedure, as predicted by the studies of Anderson and Souryal et al. (1,7). DISCUSSION Intercondylar notch stenosis is an accepted cause of both native and reconstructive ACL failure (l-8). Anderson and Souryal et al., independently, have shown with statistical certainty that bilateral, noncontact ACL ruptures occur in patients with stenotic intercondylar notches (1,7). Thus, widening notchplasty has been advocated as an essential element of ACL surgery (2,4,5,8). Tanzer and Lenczner demonstrated that notch stenosis is a relative phenomenon, dependent on the size of the cruciate ligament graft. The larger the ligament, the greater the degree of notch impingement in terminal knee extension (8). Unfortunately, parameters for optimal notch width are unknown. A review of the data conceming the size and configuration of the intercondylar notch is hardly definitive, because each study analyzed small samples and used different methodologies (1,7,8) (Tables 1 and 2). Anderson used computerized tomography (CT) to evauate the intercondylar notch and found that the normal, maximal notch-width index was 0.266 when measured from the most distal of three CT cuts of the notch. This averaged value decreased to 0.207 if measured higher in the notch, at two-thirds notch height (1). On plain-film tunnel radiographs, Souryal et al. measured the notch width at its narrowest point and TABLE 1. Comparative average notch-width index measurements (NWZ = notch width + condyle width) Souryal et al. (7)
Normal Unilateral ACL inj. Bilateral ACL inj.
FIG. 1. Bilateral tunnel-view radiographs with patients in the prone, 50” flexed Camp-Coventry position. The normative (left) knee, notch-width index is 0.227. The index is the ratio of the measured intercondylar notch width at midnotch height (20 mm) divided by the total condylar width at the level of the popliteal grove (88 mm). After arthroscopic notchplasty, the notch-width index increased to 0.289 (right).
Arthroscopy,
Vol. 7, No. 3, 1991
Anderson et al. (1) NWI’
Berg
No. of pts.
NWI”
No. of pts.
max
2/3Htd
50
0.2338
I7
0.266
0.207
-
50
0.2248
17
0.251
0.185
19
0.2214
35
O.l%I
14
0.229
0.1%
1
0.1580
No. of pts.
NWIb -
a Made from plain-film tunnel-view radiographs. Notch width was measured from the narrowest segment of the intercondylar notch. b NW1 measured at one-half notch height from plain-film tunnel radiographs. ’ Notch width was measured from the notch outlet at its widest point near its base, using computerized tomography technique. d NW1 measured at two-thirds notch-height.
ASSESSING
ARTHROSCOPIC
TABLE 2. Cudaveric notch width index measurements [Tunzer et ul. (S)] Site measured
NW1
Superior 113 Middle 113 Inferior 113
0.13 0.24 0.26
Direct caliper measurements eric specimens.
were made in 10 normal cadav-
found the normal index averaged 0.2338 (7). Many investigators have noted that notch geometry is variable (1,3,4). “Cresting wave” or inverted “V”shape notches do not reproducibly lend themselves to the Souryal measurement based on maxima1 notch narrowness. Thus, the measurements in this study were made at a more reproducible location, one-half notch height. Tanzer and Lenczner made direct caliper measurements of notch anatomy in 10 cadaveric specimens and found the ratio of notch width to condyle width to be 0.24 in the mid one-third and 0.26 in its inferior one-third (8) (Table 2). The latter figure agreed with the data of Anderson et al (I) (Table I). The beauty of the notch-width index made from tunnel knee radiographs is that it is an objective measurement readily accessible to the clinician. It is reasonable to include index measurements in the evaluation of reconstructive ACL surgery if notchplasty was performed. A synthesis of all available data on notch-width measurement and geometry suggested that the notchplasty should minimally simulate a normal 0.250 notch-width index (Table 1) when measured at midnotch height. This hypothetical goal was attained arthroscopically in 17 of 20 patients (85%). When determined by comparative notch-width index measurements to either preoperative or normal side values, the average notch-width index increased 0.06, which correlates with absolute notch widening of between 4 and 6 mm. The notch-width index calculation verified that the attempt to empirically widen the intercondylar notch by one 5.5mm burr diameter was reproducibly successful. This is the first in vivo study to quantify the amount of intercondylar notchplasty attained by arthroscopic means, Definition of optimal notch-width values can only be made when further measurements are correlated
NOTCHPLASTY
277
with clinical results. The study supports the observation that stenotic intercondylar notches are associated with bilateral ACL injuries (1.7), because one patient with a notch-width index below 0.180 developed a noncontact ACL injury 7 months after reconstruction had been performed on the contralatera1 side. In one patient followed for 1% years, early osteophyte formation at the margins of the intercondylar notch was noted on a second-look arthroscopy. A second postoperative tunnel radiograph demonstrated no appreciable change in the notch-width index measurement (0.287 at 3 months versus 0.281 at 19 months). It was deduced that the osteophytes must have been primarily cartilaginous and not bony, yet this finding raises the concern that notch stenosis may recur with time to cause abrasive cruciate graft attrition and late reconstructive failure. Serial intercondylar notch observations with lengthy clinical follow-up are needed to address this concern. Acknowledgment: I thank Kathleen M. Quigley R.N., B.S.N., and Lynn Smith for supererogatory help with this article.
REFERENCES 1. Anderson
2.
3.
4. 5 6. 7.
8.
9.
AF, Lipscomb AB, Liudahl KJ, Addlestone RB. Analysis of the intercondylar notch by computed tomography. Am J Sports Med 1983;15:547-52. Clark JA, Howell SM. Tibia1 tunnel placement in isometric anterior cruciate ligament reconstructions and its role in producing graft impingement. AAOS presentation February 9, 1990, New Orleans. Houseworth SW, Mauro UJ, Mellon BA. Kieffer DA. The intercondylar notch in acute tears of the anterior cruciate ligament: a computer graphics study. Am J Sports Med 1987;15:2214. Kieffer DA, Curnow RJ, Southwell RB, et al. Anterior cru&ate ligament arthroplasty. Am J Sports Med 1984;12:30112. Muller W. The knee: Form function and ligament reconstruction. New York: Springer Verlag, 1983. Norwood LA, Cross MJ. The intercondylar shelf and the anterior cruciate ligament. Am J Sports Med 1977;5:1714. Souryal TO, Moore HA, Evans JP. Bilaterality in anterior cruciate ligament injuries: associated intercondylar notch stenosis. Am J Sports Med 1988;16:449-54. Tanzer M, Lenczner E. The relationship of intercondylar notch size and content to notchplasty requirement in anterior cruciate ligament surgery. Arzhroscopy 1990;6:89-93. Merrill V. Atlas of roentgenographic positions and standard radiologic procedures, 4th ed, vol 1. St. Louis: CV Mosby, 1975:99.
Arthmcopy,
Vol. 7, No. 3. 1991
Assessing Arthroscopic
Notchplasty
Eugene E. Berg, M.D. ~_
.~_.
Summary: To evaluate the ability to perform a widening arthroscopic
intercondylar notchplasty as part of an anterior cruciate ligament reconstruction, 20 patients had notch-width index measurements compared with either preoperative or normal-side values. The notch-width index increased an average of 0.062, correlating with absolute notch widening of 4-6 mm. This study provides
in vivo evidence that notchplasty widening can be reproducibly performed arthroscopically. The optimal notch width for reconstructive anterior cruciate ligament surgery has yet to be determined. Key Words: Notchplasty-Anterior cruciate ligament-Notch width.
reconstruction. There were 14 male and 6 female patients, whose age averaged 26% years at the time of surgery (range 17-35 years). Twelve reconstructions were performed for chronic instability, and eight were done acutely within 3 weeks of injury. Half of the patients (10) sustained noncontact injuries. Nine patients had had 12 previous procedures, none of which had included a notchplasty. All tunnel radiographic views were made with patients prone, in the 50” knee flexion, CampCoventry position (9). Six patients had preoperative tunnel views of the affected knee and these radiographs were used preferentially for comparison. The remaining patients had bilateral tunnel views obtained at maximum follow-up in which the operative knee was compared with the uninvolved side. Postoperative follow-up ranged from 6 months to 21/2 years and averaged 17 months. All patients underwent a free autogenous patellar tendon, ACL reconstruction under arthroscopic control. The notchplasty was performed with 5.5 mm-diameter spherical abrasion burr. A notchplasty of at least one burr diameter was made from the anterior aspect of the lateral intercondylar notch at its articular cartilage margin and was continued posteriorly to the condylar dropoff point. Notch-width index measurements similar to that described by Anderson and Souryal et al. were used to determine the extent of the arthroscopic inter-
The relationship of the anterior cruciate ligament (ACL) to the intercondylar notch has a significant bearing on the pathomechanics of ACL injury and its reconstruction (l-8). Norwood and Cross were the first to note that the ACL contacts the intercondylar notch when the knee is in hyperextension (6). This mechanism concentrates stress in the middle one-third of the ligament and is a cause of interstitial failure. Independent studies by Anderson and Souryal, with strong statistical correlations, confirmed that bilateral ACL ruptures occur in individuals with stenotic intercondylar notches (1,7). Thus, a wide notchplasty to prevent abrasive graft attrition has become a critical element of ACL reconstructive surgery (2,4,8). This study was undertaken to document whether a widening notchplasty can be effected reproducibly by arthroscopic methods. MATERIALS AND METHODS Bilateral tunnel knee radiographs were obtained in 20 patients who had unilateral, arthroscopic ACL From the Department of Orthopaedics, U.S.C. School of Medicine, Columbia, South Carolina, U.S.A. Address correspondence and reprint requests to Dr. E. E. Berg at Department of Orthopaedics, U.S.C. School of Medicine, Two Richland Medical Park, Suite 404, Columbia, SC 29203, U.S.A.
275
276
E. E. BERG
condylar notchplasty (1,7). The notch-width index is a ratio of measured intercondylar notch width in its middle one-third, to the width of both femoral condyles at the level of the popliteal groove on tunnel-view radiographs (7) (Fig. 1). The measurement is expressed as a ratio to minimize differences in radiographic magnification and technique. RESULTS Preoperative or normative side notch-width indices ranged from 0.158 to 0.284 and averaged 0.218. Four notch-width indices (20%) measured less than 0.200, and 10 measured less than 0.220. The postoperative notch-width index ranged from 0.225 to 0.326 and averaged 0.280. Thus, the mean index improved from a preoperative value of 0.218 to 0.280 postoperatively, increasing 0.062. The increase in notch-width index ranged from 0.032 to 0.119. If raw measurements were reduced by a 20% radiographic magnification factor, the mean index improvement of 0.062 correlates with actual notch widening of between 4 and 6 mm. Postoperatively, 17 patients had a notch-width index greater than 0.250, and only three were less than this amount. Interestingly, the patient with the narrowest nor-
mative notch-width index of 0.158 incurred a contralateral, noncontact ACL injury 7 months after the index procedure, as predicted by the studies of Anderson and Souryal et al. (1,7). DISCUSSION Intercondylar notch stenosis is an accepted cause of both native and reconstructive ACL failure (l-8). Anderson and Souryal et al., independently, have shown with statistical certainty that bilateral, noncontact ACL ruptures occur in patients with stenotic intercondylar notches (1,7). Thus, widening notchplasty has been advocated as an essential element of ACL surgery (2,4,5,8). Tanzer and Lenczner demonstrated that notch stenosis is a relative phenomenon, dependent on the size of the cruciate ligament graft. The larger the ligament, the greater the degree of notch impingement in terminal knee extension (8). Unfortunately, parameters for optimal notch width are unknown. A review of the data conceming the size and configuration of the intercondylar notch is hardly definitive, because each study analyzed small samples and used different methodologies (1,7,8) (Tables 1 and 2). Anderson used computerized tomography (CT) to evauate the intercondylar notch and found that the normal, maximal notch-width index was 0.266 when measured from the most distal of three CT cuts of the notch. This averaged value decreased to 0.207 if measured higher in the notch, at two-thirds notch height (1). On plain-film tunnel radiographs, Souryal et al. measured the notch width at its narrowest point and TABLE 1. Comparative average notch-width index measurements (NWZ = notch width + condyle width) Souryal et al. (7)
Normal Unilateral ACL inj. Bilateral ACL inj.
FIG. 1. Bilateral tunnel-view radiographs with patients in the prone, 50” flexed Camp-Coventry position. The normative (left) knee, notch-width index is 0.227. The index is the ratio of the measured intercondylar notch width at midnotch height (20 mm) divided by the total condylar width at the level of the popliteal grove (88 mm). After arthroscopic notchplasty, the notch-width index increased to 0.289 (right).
Arthroscopy,
Vol. 7, No. 3, 1991
Anderson et al. (1) NWI’
Berg
No. of pts.
NWI”
No. of pts.
max
2/3Htd
50
0.2338
I7
0.266
0.207
-
50
0.2248
17
0.251
0.185
19
0.2214
35
O.l%I
14
0.229
0.1%
1
0.1580
No. of pts.
NWIb -
a Made from plain-film tunnel-view radiographs. Notch width was measured from the narrowest segment of the intercondylar notch. b NW1 measured at one-half notch height from plain-film tunnel radiographs. ’ Notch width was measured from the notch outlet at its widest point near its base, using computerized tomography technique. d NW1 measured at two-thirds notch-height.
ASSESSING
ARTHROSCOPIC
TABLE 2. Cudaveric notch width index measurements [Tunzer et ul. (S)] Site measured
NW1
Superior 113 Middle 113 Inferior 113
0.13 0.24 0.26
Direct caliper measurements eric specimens.
were made in 10 normal cadav-
found the normal index averaged 0.2338 (7). Many investigators have noted that notch geometry is variable (1,3,4). “Cresting wave” or inverted “V”shape notches do not reproducibly lend themselves to the Souryal measurement based on maxima1 notch narrowness. Thus, the measurements in this study were made at a more reproducible location, one-half notch height. Tanzer and Lenczner made direct caliper measurements of notch anatomy in 10 cadaveric specimens and found the ratio of notch width to condyle width to be 0.24 in the mid one-third and 0.26 in its inferior one-third (8) (Table 2). The latter figure agreed with the data of Anderson et al (I) (Table I). The beauty of the notch-width index made from tunnel knee radiographs is that it is an objective measurement readily accessible to the clinician. It is reasonable to include index measurements in the evaluation of reconstructive ACL surgery if notchplasty was performed. A synthesis of all available data on notch-width measurement and geometry suggested that the notchplasty should minimally simulate a normal 0.250 notch-width index (Table 1) when measured at midnotch height. This hypothetical goal was attained arthroscopically in 17 of 20 patients (85%). When determined by comparative notch-width index measurements to either preoperative or normal side values, the average notch-width index increased 0.06, which correlates with absolute notch widening of between 4 and 6 mm. The notch-width index calculation verified that the attempt to empirically widen the intercondylar notch by one 5.5mm burr diameter was reproducibly successful. This is the first in vivo study to quantify the amount of intercondylar notchplasty attained by arthroscopic means, Definition of optimal notch-width values can only be made when further measurements are correlated
NOTCHPLASTY
277
with clinical results. The study supports the observation that stenotic intercondylar notches are associated with bilateral ACL injuries (1.7), because one patient with a notch-width index below 0.180 developed a noncontact ACL injury 7 months after reconstruction had been performed on the contralatera1 side. In one patient followed for 1% years, early osteophyte formation at the margins of the intercondylar notch was noted on a second-look arthroscopy. A second postoperative tunnel radiograph demonstrated no appreciable change in the notch-width index measurement (0.287 at 3 months versus 0.281 at 19 months). It was deduced that the osteophytes must have been primarily cartilaginous and not bony, yet this finding raises the concern that notch stenosis may recur with time to cause abrasive cruciate graft attrition and late reconstructive failure. Serial intercondylar notch observations with lengthy clinical follow-up are needed to address this concern. Acknowledgment: I thank Kathleen M. Quigley R.N., B.S.N., and Lynn Smith for supererogatory help with this article.
REFERENCES 1. Anderson
2.
3.
4. 5 6. 7.
8.
9.
AF, Lipscomb AB, Liudahl KJ, Addlestone RB. Analysis of the intercondylar notch by computed tomography. Am J Sports Med 1983;15:547-52. Clark JA, Howell SM. Tibia1 tunnel placement in isometric anterior cruciate ligament reconstructions and its role in producing graft impingement. AAOS presentation February 9, 1990, New Orleans. Houseworth SW, Mauro UJ, Mellon BA. Kieffer DA. The intercondylar notch in acute tears of the anterior cruciate ligament: a computer graphics study. Am J Sports Med 1987;15:2214. Kieffer DA, Curnow RJ, Southwell RB, et al. Anterior cru&ate ligament arthroplasty. Am J Sports Med 1984;12:30112. Muller W. The knee: Form function and ligament reconstruction. New York: Springer Verlag, 1983. Norwood LA, Cross MJ. The intercondylar shelf and the anterior cruciate ligament. Am J Sports Med 1977;5:1714. Souryal TO, Moore HA, Evans JP. Bilaterality in anterior cruciate ligament injuries: associated intercondylar notch stenosis. Am J Sports Med 1988;16:449-54. Tanzer M, Lenczner E. The relationship of intercondylar notch size and content to notchplasty requirement in anterior cruciate ligament surgery. Arzhroscopy 1990;6:89-93. Merrill V. Atlas of roentgenographic positions and standard radiologic procedures, 4th ed, vol 1. St. Louis: CV Mosby, 1975:99.
Arthmcopy,
Vol. 7, No. 3. 1991