Arthroscopy:
The Journal of Arthroscopic
and Related Surgery
Published by Raven Press, Ltd. 0 1992 Arthroscopy
8(3):321-334
Association of North America
Preoperative Computed Tomography Scanning and Arthroscopy in Predicting Outcome after Lateral Retinacular Release Kevin P. Shea, M.D., and John P. Fulkerson,
M.D.
Summary: We initiated a study to look at preoperative, flexed-knee, midpatellar computed tomography (CT) scans and intraoperative arthroscopic findings of lateral patellar articular degeneration in predicting the results after lateral retinacular release for failed nonoperative treatment of anterior knee pain. Twenty patients with 30 painful knees underwent preoperative flexedknee, midpatellar CT scans that were retrospectively classified by the method of Fulkerson into normal alignment, lateral subluxation, lateral patellar tilt, and combined tilt and subluxation. Arthroscopy was performed before open lateral release. The lateral facet of the patella was graded as either minimal changes (Outerbridge I or II) or advanced (Outerbridge III or IV) changes. Patients were followed for a minimum of 2 years and graded on a standard patellofemoral rating scale. Only 22 of 30 knees that were thought to be clinically malaligned, actually were malaligned by CT scan; eight CT scans were interpreted as normal. The results were further stratified into group A (CT-documented tilt, minimal facet changes), group B (CT-documented tilt, advanced facet changes), and group C (normal CT). Ninety-two percent of group A were rated good or excellent. Twenty-two percent of Group B rated good/excellent, 33% fair, 44% poor. Only 13% of group C rated good (one patient). Based on the results of the study, we recommend lateral release for anterior knee patients with CT-proven patellar tilt who have not responded to conservative treatment and have minimal facet changes with minimal or no subluxation. Lateral retinacular release should not be offered as a treatment to the patient with a normally aligned patella because poor results will most likely result. Key Words: Computed tomography scan-Patellar tilt-Patellar subluxation.
ment for excessive lateral facet pressure syndrome, otherwise known as lateral patellar tilt. In theory, lateral release relieves the excessive retinacular strain and restores a laterally tilted patella to normal alignment. Theoretically, it also eliminates excessive lateral patellar tethering, which has been implicated in recurrent patellar subluxation. Thus, lateral release is a realignment procedure used to biomechanically correct patellar malalignment . The key to treating anterior knee pain with lateral release is to recognize which symptomatic patellae are malaligned and which are not. Numerous his-
release (lateral release) is the most commonly performed surgical procedure used to treat anterior knee pain that has not responded to conservative treatment. Merchant (1) first described lateral release as a surgical treatment for recurrent patellar subluxation. Later, Larson et al. (2) described the use of lateral release as a treatLateral
retinacular
From the Department of Orthopaedics, University of Connecticut School of Medicine, Farmington, Connecticut, U.S.A. Address correspondence and reprint requests to Dr. Kevin P. Shea, Assistant Professor of Orthopaedics, University of Connecticut School of Medicine, Farmington, CT 06034, U.S.A.
327
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torical symptoms and physical signs (3-16), as well as radiographic techniques (17-19), have been reported in the literature as indicative of patellar malalignment. However, using these preoperative indicators of patellar malalignment, success after lateral release has been, at best, inconsistent. In 1986, Schutzer et al. (20) described the use of midpatellar, lO-20”, knee-flexed computed tomography (CT) scanning to accurately document patellar (mal)alignment. They stressed that the CT scan be imaged through the midpatellofemoral joint because this is the area of articular cartilage force transfer. Three patterns of patellofemoral malalignment were described (Fig. 1). Subluxation is defined as any lateral deviation of the patellar apex from the bisector of the femoral sulcus angle. Tilt is defined by the patellar tilt angle, the angle formed by a line parallel to the lateral facet and the line connecting the posterior femoral condyles, being 7” or less. A combined subluxation and tilt pattern was also described. This study was undertaken to correlate preoperative CT scan data with outcome after lateral release in a group of patients with resistant anterior knee pain. A secondary aim was to investigate what effect degenerative changes in the patellar articular cartilage have on outcome after lateral release in these same patients.
45 PATIENTS 1 - Subluxation
Ll L
FIG. 1. Patellofemoral malalignment patterns in patients with patellofemoral pain as demonstrated by CT scanning. Reprinted with permission (31).
Vol. 8, No. 3, 1992
Twenty patients 16-43 years of age underwent a total of 30 lateral releases for resistant anterior knee pain. All knees were judged clinically to have patellar malalignment. Malalignment was felt to be the cause of the knee pain. The previously described midpatellar CT scans were performed on all knees before surgery. However, the decision to perform lateral release was based strictly on the patient’s symptoms and the clinical impression of patellar malalignment . Arthroscopic evaluation was performed before lateral release. The degeneration of the lateral facet articular cartilage was graded as minimal if it displayed Outerbridge I or II changes or advanced if it displayed Outerbridge III or IV changes (21). The lateral release was then performed through a 2-cm longitudinal incision immediately lateral to the patella. The retinaculum was incised from the fatty plane between the longitudinal fibers of the vastus lateralis and the muscle’s more oblique fibers (22) superiorly and to the tibia1 tubercle inferiorly (Fig. 2). Care was taken not to damage the lateral meniscus. The tourniquet was let down and hemostasis achieved with electrocautery. A complete release was assured if the patella could be everted 90%. Only the skin was closed. Rehabilitation began several days after surgery and continued until full range of motion and adequate muscle strength was achieved. The patients were followed for a minimum of 2 years (range 2-6.25, average 3.75). At the time of last follow-up, patients were rated on a previously used patellofemoral rating scale as good/excellent, fair or poor (Table 1) (20). Any patient requiring further surgery for anterior knee pain was rated poor. Final ratings were then compared with the preoperative CT scan alignment pattern and intraoperative cartilage classification.
M
Type 3 - Tilt without subluxation 19 Patients, 25 Knees
Arthroscopy,
METHODS
RESULTS A complete summary of the data is provided in Table 2. Overall, 50% of the operated knees were rated good/excellent, 27% fair, and 23% poor at the time of last follow-up. Twenty-two knee CT scans displayed excessive patellar tilt with or without patellar subluxation i.e., type II or III in Fulkerson’s (20) classification. No knees with pure subluxation [Fulkerson (20), type I] were in this study. Eight
LATERAL
RETINACULAR
RELEASE
329
developed reflex sympathetic dystrophy in the postoperative period. Three representative cases, one from each group, will further illustrate the value of preoperative CT scanning and arthroscopy in predicting outcome of lateral release. Case 1 A 21-year-old college student presented with a Syear history of anterior knee pain that was not responsive to conservative measures and was considered for a lateral release. Her preoperative CT scan had a patellar tilt angle of 0” (normal 8’) as
TABLE 1. Patellofemoral joint evaluation scale Points
FIG. 2. The extent of open lateral release used by the authors. The subcutaneous incision extends from the tibia1 tubercle inferiorly through the lateral retinacular fibers and extends into the fatty plane between the vastus lateralis and the more oblique fibers of the vastus lateralis obliquus.
knees had normal CT scans, that is, no lateral patellar tilt or patellar subluxation. The data were than subdivided into three groups according to the CT scan classification (patellar tilt or normal) and the degree of articular cartilage degeneration (minimal or advanced). Group A was composed of 13 knees with CT-documented tilt and minimal articular cartilage changes. Group B was composed of nine knees with CT-documented tilt and advanced articular cartilage changes. Group C was composed of eight knees with a normal CT. This group contained too few knees to further subdivide according to articular cartilage degeneration. Ninety-two percent of group A knees were rated good/excellent and 8% (one patient) rated poor at follow-up. Twenty-two percent of group B knees were rated good/excellent, 33% fair, and 44% poor. Only one patient (13%) from group C was rated good/excellent, with 50% rated fair, and 37% poor at the time of follow-up. Two group C knees (25%)
Limp None Slight/episodic Severe Assistive devices None Cane or brace Unable to bear weight Stair climbing No problem Slight impairment Very slowly One step at a time Unable Crepitation None Annoying Limits activities Severe Instability, “Giving way” Never Occasionally with vigorous activity Frequently with vigorous activities Occasionally with daily activity Frequently with daily activity Every day Swelling None After vigorous activity only After walking or mild activity Constant Pain None Occasionally with vigorous activity Marked with vigorous activity Marked after walking 1 mile or mild/moderate rest pain Marked with walking < 1 mile Constant and severe
5 3 0 5 3 0 20 15 10 5 0 5 3 2 0 20 10 8 5 2 0 10 5 2 0 35 30 20 15 10 0
This patellofemoral rating scale is currently in place at the Department of Orthopaedic Surgery, Division of Sports Medicine, University of Connecticut School of Medicine, Farmington, Connecticut, U.S.A. Total points possible: 100.
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330
K. P. SHEA AND J. P. FULKERSON TABLE 2. Comparison
between preoperative
Patients
No. of Knees
All Normal CT” CT-documented tilt” Minimal facet changes* Advanced facet changesb
30 8 22 13 9
CT scanning and outcome after lateral release
Average years of age (range)
Average months of follow-up (range)
27 (16-43) 23 (16-33) 24 (lW3)
43 (24-75) 51 (48-75) 40 (24-58)
Excellent/Good 15 1 14 12 2
Fair
Poor
7 4 3 0 3
8 3 5 1 4
D According to Schutzer et al. (20). b See text for explanation.
shown in Fig. 3A. At arthroscopy, the lateral patellar facet was softened, but no breaks in the articular surface were noted (Outerbridge I). Six weeks after lateral release, her postoperative CT scan showed a patellar tilt angle of 17” (Fig. 3B), which is normal. Her knee rated excellent at 3-year follow-up. Case 2 A 20-year-old woman presented with a 7-year history of anterior knee pain that persisted despite activity modification, physical therapy, and bracing. On physical examination, her lateral retinaculum was tender and tight. The patellar tilt angle was - 5” on the preoperative CT scan (Fig. 4A). Arthroscopically, the lateral patellar facet was graded Outerbridge III (advanced changes). Six weeks later, her CT scan showed a patellar tilt angle of 6” (some correction as compared with the preoperative CT
scan, but still abnormal) fair at 4-year follow-up.
(Fig. 4B). She was rated
Case 3 A 20-year-old college student complained of severe anterior knee pain for 1 year. All conservative measures had failed to relieve her symptoms. The preoperative CT scan was normal (Fig. 5A). Arthroscopically , her lateral facet showed minimal changes. The postoperative CT scan was identical to the preoperative scan (Fig. SB). She was rated poor at 2-year follow-up.
DISCUSSION Although there are many causes of anterior knee pain, they can be divided into two main subsets:
3A,B
FIG. 3. A preoperative CT scan (PTA, O”)(A) showing patellar tilt and a postoperative CT scan (PTA, 17”)(B) 5 weeks later showing a normal patellar tilt angle.
Arthroscopy,
Vol. 8, No. 3, 1992
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RETINACULAR
331
RELEASE
FIG. 4. A preoperative CT scan showing a patellar tilt angle of - 15” (A) and a postoperative CT scan showing a patellar tilt angle of 6” (B). which is clearly improved over A but still abnormal.
those in which the patella is normally aligned, and those in which the patella is malaligned. Patellar malalignment can be further divided into two basic types: those with lateral patellar subluxation, and those with excessive lateral patellar tilt. Schutzer and Fulkerson (20) identified a group in which both malalignment patterns coexist. At this
time, it is unclear whether medial patellar subluxation and/or medial patellar tilt exist other than as complications of surgery. Twenty-two knees in this series had CT scanidentified lateral patellar tilt with or without combined patellar subluxation. The syndrome of excessive lateral patellar pressure (ELPS) was first de-
5. A scan which normal (PTA, W), and a postoperative CT which indicates no change in patellofemoral alignment has taken place (F’TA, 15”).
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K. P. SHEA AND J. P. FULKERSON
scribed by Ficat (23). In this syndrome, the lateral retinaculum becomes excessively tight, resulting in a lateral tilting of the patella. As knee flexion progresses, the patella is forced into a congruent reduction in the femoral trochlea, which then stretches the shortened lateral retinaculum. Pain in the lateral retinaculum results from stretching of this tightened tissue. The tilting of the patella increases the joint reaction force across the lateral facet, which may eventually lead to cartilage breakdown. Fulkerson (24) has demonstrated microscopic neuromata in the lateral retinaculum that presumably result from excessive stretching of the tight tissue. Continued stretching and irritation of the lateral retinaculum creates inflammation, scarring, and contracture of the lateral retinaculum, which increases patellar tilt and further increases contact pressures in the lateral patellar facet. The key to treatment of this early ELPS knee is early lateral retinacular release to relieve excessive pressure on the lateral facet in order to prevent articular cartilage breakdown. Realignment of the patellofemoral joint, before excessive lateral facet breakdown occurs, should restore the patella to normal alignment and give the best chance of an excellent long-term result. This study supports this theory. Lateral retinacular release was performed on 13 knees with minimal articular cartilage changes and preoperative CT scan evidence of lateral patellar tilt; 12 were rated good/excellent at >Zyear follow-up. It is unclear why one patient failed to respond to this treatment. That patient ultimately was rated excellent after a tibia1 tubercle anteriorization procedure, so we presume the degree of articular cartilage injury was more extensive than was recorded at the time of arthroscopy. Based on these results, we endorse lateral retinacular release in the fashion described for any patient with anterior knee pain, excessive lateral patellar tilt on a preoperative scan, and minimal articular cartilage changes (i.e., Outerbridge grade I or II) who have failed conservative treatment (Fig. 3A and B). Once articular cartilage breakdown occurs in ELPS, collapse in the lateral facet occurs. Facet collapse decreases the height of the lateral patella, which reduces strain on the lateral retinaculum. Although the lateral retinaculum may remain tight, pain now begins to emanate directly from the degenerated patella. Whereas lateral retinacular release may provide relief in many of these patients, lateral release frequently fails to restore the patella Arthroscopy,
Vol. 8, No. 3, 1992
to normal alignment because the patella and femoral trochlea are no longer congruent. Progressive degeneration in the lateral patellar facet may occur, and diminishing satisfaction after lateral release may be seen with time. Huberti and Hayes (25) have demonstrated that cadaver knees with extensive involvement of the lateral patellar facet show no changes in patellofemoral contact stress with lateral retinacular release. The results of this study support this theory as well. Only two of nine knees with extensive lateral facet changes were rated good or excellent at a 22year follow-up. In discussing each patient’s postoperative course at the final follow-up evaluation, many initially benefited from the procedure. However, the results deteriorated with time. Based on these results, we still recommend lateral retinacular release selectively in patients with preoperative CT scan-documented patellar tilt and arthroscopic evidence of grade 3 lateral facet changes. The surgeon should caution the patient if extensive damage is seen in the lateral patellar facet results may deteriorate with time (26). Lateral patellar subluxation until recently has been recognized as the cause of a great majority of anterior knee pain in the malaligned patellofemoral joint. Hughston (17), Insall (9), and Merchant (19) all have described radiographic criteria that would identify lateral patellar subluxation and all have recommended patellar realignment as treatment of these conditions. They all emphasize that although the classic patient with subluxation will have episodes of patellar giving-way or frank dislocations, many of these patients do not present with instability symptoms, but with pain after excessive activities. In the current study, there was only one patient in 44 scanned who had an isolated lateral subluxation pattern. Although we felt it was interesting that given so many patients with anterior knee pain, only one with isolated lateral patellar subluxation could be identified, no comment could be made with regard to the results of lateral retinacular release in these patients. The major causes of anterior knee pain with a normally aligned patella are postoperative neuroma, traumatic chondromalacia patella, arthritis, pain after patella fracture, and reflex sympathetic dystrophy, as well as overuse disorders such as Osgood-Schlatters disease and Sinding-LarssonJohanssen syndrome. Many of the soft tissue overuse syndromes will respond to conservative treatment including avoidance of provocative activities,
LATERAL
RETINACULAR
rest, and physical therapy. The common thread among the others (i.e., traumatic chondromalacia, idiopathic chondromalacia, and arthritis) is global destruction of the articular cartilage of the patella. There is no one area of focal stress overload in these disorders. The etiology of the pain in these disorders is unknown, but pain is presumed to emanate from the patella itself. Identification of patients with these normal alignment patellar disorders is frequently difficult. Most will have a typical onset of blunt trauma to the anterior knee and a prolonged course of knee pain that has been unresponsive to all other forms of treatment. Many of these patients will be workers’ compensation patients or involved in litigation after motor vehicular accidents, which will further cloud the issue. When conservative management fails, lateral release has been entertained as a possible treatment for relief of pain. However, because there is no focal stress overload in the patellofemoral joint, lateral release will uniformly fail. Huberti and Hayes (27) have demonstrated in a cadaver model that knees with presumably normal patellofemoral alignment do not undergo any stress alterations in the patellofemoral joint with lateral retinacular release. The data in this study support these conclusions. Of the eight patients with long-standing anterior knee pain that was not responsive to conservative treatment, seven patients either failed to improve or became worse after lateral retinacular release. This was true regardless of the severity of articular cartilage degeneration in the patella. Nine other patients with anterior knee pain and normal midpatellar transverse CT scans were seen during the study, but were not offered lateral release (28). When these patients were contacted later, they all had received lateral retinacular release at other institutions. All nine of these patients were also rated as having a poor long-term result on the patellofemoral rating scale. Therefore, we do not recommend lateral release in patients with anterior knee pain but a normally aligned patella. This study emphasizes the importance of preoperative CT scan in selecting those patients who are most likely to improve with lateral retinacular release. However, we do not recommend a patellofemoral CT scan on every patient with anterior knee pain. Instead, we recommend that a CT scan be performed only after the patient has failed what the surgeon believes is an extensive conservative treatment program and is considering surgical treatment. Midpatellofemoral CT scans (29) are then ordered
333
RELEASE
and only those patients with documented malalignment are offered realignment surgery. This study does not support any one treatment for the painful but normally aligned patella. Instead, it only offers experiential evidence that lateral retinacular release performed without preoperative tilt will not relieve pain in many cases. In fact, several of the patients were made worse by this procedure. SUMMARY In summary, the current study demonstrates that the use of preoperative CT scanning is essential to identify whether patellar malalignment exists before surgical lateral release. In those patients with CTdocumented tilt and minimal articular cartilage degeneration as seen at the time of surgery, lateral retinacular release was shown to produce >90% good or excellent results at >2-year follow-up. In those patients with CT-documented tilt and extensive lateral facet changes, the long-term results of lateral release were not as good, but we still recommend the procedure as a first-line attempt to relieve patellofemoral pain in selected patients. In those patients with a normally aligned patella on the preoperative CT scan, we do not recommend lateral retinacular release, because little benefit can be expected. Further investigations are needed to identify the optimal procedure for the normally aligned but painful patella and those patients who have extensive lateral facet changes when first seen by their surgeon. REFERENCES 1. Merchant AC, Mercer RL. Lateral release of the patella. Clin Orthop
1974;103:40-5.
2. Larson RL, Cabaud HE, Slocum DB, James SL, Keenan T, Hutchinson T. The patellar compression syndrome: surgical treatment by lateral retinacular release. Clin Orthop 1978; 134:1%x-67. 3. Betz R, Magi11J, Lonergan R. The percutaneous lateral retinacular release. Am J Sports Med 1987;15:477-82. 4. Christensen F, Sballe K, Snerum L. Treatment of chondromalacia patellae by lateral retinacular release of the patella. C/in Or&p 1988;234: 145-7. 5. Dzioba RB, Strokon A, Mulbry L. Diagnostic arthroscopy and longitudinal open lateral release arthroscopy. 1985; 1: 131-5. 6. Grana WA, Hinkley B, Hollingsworth S. Arthroscopic evaluation and treatment of patellar malalignment. Chin Orthop 1984;86:122-8. I. Harwin SF, Stem RE. Subcutaneous lateral retinacular release for chondromalacia patellae. Clin Orthop 1981;156: 207-10. 8. Henry JH, Goletz TH, Williamson B. Lateral retinacular
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9.
10.
11. 12.
13. 14. 15.
16.
17. 18.
release in patellofemoral subluxation. Am J Sports Med 1986;14: 121-9. Insall J. Current concepts review: patellar pain. JBone Joint Surg 1982;64A:l47-52. Krompinger WJ, Fulkerson JP. Lateral retinacular release for intractable lateral retinacular pain. Clin Orrhop 1983;179: 191-3. McGinty JB, McCarthy JC. Endoscopic lateral retinacular release. Clin Orrhop 1981;158: 120-5. Metcalf RW. An arthroscopic method for lateral release of the subluxating or dislocating patella. Chin Orthop 1982;167: 9-18. Osborne AH, Fulford PC. Lateral release for chondromalacia patellae. J Bone Joint Surg 1982;64B:202-5. Schonholtz GJ, Zahn MG, Magee CM. Lateral retinacular release of the patella. Arthroscopy 1987;3:26%72. Sherman OH, Fox JM, Sperling H, et al. Patellar instability: treatment by arthroscopic electrosurgical lateral release. Arthroscopy 1987;3: 152-60. Strand T, Alho A, Raugstad T, Bjersand AJ. Patellofemoral disorders treated by operations. Ac?a Orthop Stand 1983; 54:914-6. Hughston JC. Subluxation of the patella. J Bone Joint Surg 1968;50A: 1003. Laurin CA, Dussault R, Levesque HP. The tangential x-ray investigation of the patellofemoral joint. Clin Orthop 1979; 144:16-26.
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19. Merchant AC, Mercer RL, Jacobsen RH, Cool CR. Roentgenographic analysis of patellofemoral congruence. J Bone Joint Surg 1974;56A:l391. 20. Schutzer SF, Ramsby GA, Fulkerson JP. The evaluation of patellofemoral pain using computerized tomography. Clin Orthop 1986;204:286-93. 21. Outerbridge RE. The etiology of chondromalacia patellae. J Bone Joint Surg 1961;43B:752-7. 22. Hallisey M, Doherty N, Bennett W, Fulkerson J. Anatomy of the junction of the vastus lateralis tendon and the patella. J Bone Joint Surg 1987;69A:545. 23. Ficat C, Bailleux A. Syndrome d’hyperpression externe de la rotale (SHPE). Rev Chir Orrhop 1975;61:139-59. 24. Fulkerson JP, Tennant R, Jaivin J, Grunnet M. Histologic evidence of retinacular nerve injury associated with patellofemoral malalignment. C/in Orthop 1985;187: 196-205. 25. Huberti H, Hayes W. Patellofemoral contact pressures. J Bone Joint Surg 1985;66A:715-24. 26. Fulkerson J. Anteromedialization of the tibia1 tuberosity for patellofemoral malalignment. C/in Orthop 1983;177: 176-81. 27. Huberti H, Hayes W. Contact pressures in chondromalacia patellae and the effects of capsular reconstructive procedures. J Orthop Res 1988;6:499-508. 28. Bernstein R, Fulkerson JP. Unpublished data. 29. Fulkerson J, Hungerford D. Disorders of the patellofemoral joint. Baltimore, Maryland: Williams & Wilkins, 1990.
The Journal of Arthroscopic
and Related Surgery
Published by Raven Press, Ltd. 0 1992 Arthroscopy
8(3):321-334
Association of North America
Preoperative Computed Tomography Scanning and Arthroscopy in Predicting Outcome after Lateral Retinacular Release Kevin P. Shea, M.D., and John P. Fulkerson,
M.D.
Summary: We initiated a study to look at preoperative, flexed-knee, midpatellar computed tomography (CT) scans and intraoperative arthroscopic findings of lateral patellar articular degeneration in predicting the results after lateral retinacular release for failed nonoperative treatment of anterior knee pain. Twenty patients with 30 painful knees underwent preoperative flexedknee, midpatellar CT scans that were retrospectively classified by the method of Fulkerson into normal alignment, lateral subluxation, lateral patellar tilt, and combined tilt and subluxation. Arthroscopy was performed before open lateral release. The lateral facet of the patella was graded as either minimal changes (Outerbridge I or II) or advanced (Outerbridge III or IV) changes. Patients were followed for a minimum of 2 years and graded on a standard patellofemoral rating scale. Only 22 of 30 knees that were thought to be clinically malaligned, actually were malaligned by CT scan; eight CT scans were interpreted as normal. The results were further stratified into group A (CT-documented tilt, minimal facet changes), group B (CT-documented tilt, advanced facet changes), and group C (normal CT). Ninety-two percent of group A were rated good or excellent. Twenty-two percent of Group B rated good/excellent, 33% fair, 44% poor. Only 13% of group C rated good (one patient). Based on the results of the study, we recommend lateral release for anterior knee patients with CT-proven patellar tilt who have not responded to conservative treatment and have minimal facet changes with minimal or no subluxation. Lateral retinacular release should not be offered as a treatment to the patient with a normally aligned patella because poor results will most likely result. Key Words: Computed tomography scan-Patellar tilt-Patellar subluxation.
ment for excessive lateral facet pressure syndrome, otherwise known as lateral patellar tilt. In theory, lateral release relieves the excessive retinacular strain and restores a laterally tilted patella to normal alignment. Theoretically, it also eliminates excessive lateral patellar tethering, which has been implicated in recurrent patellar subluxation. Thus, lateral release is a realignment procedure used to biomechanically correct patellar malalignment . The key to treating anterior knee pain with lateral release is to recognize which symptomatic patellae are malaligned and which are not. Numerous his-
release (lateral release) is the most commonly performed surgical procedure used to treat anterior knee pain that has not responded to conservative treatment. Merchant (1) first described lateral release as a surgical treatment for recurrent patellar subluxation. Later, Larson et al. (2) described the use of lateral release as a treatLateral
retinacular
From the Department of Orthopaedics, University of Connecticut School of Medicine, Farmington, Connecticut, U.S.A. Address correspondence and reprint requests to Dr. Kevin P. Shea, Assistant Professor of Orthopaedics, University of Connecticut School of Medicine, Farmington, CT 06034, U.S.A.
327
328
K. P. SHEA AND J. P. FULKERSON
torical symptoms and physical signs (3-16), as well as radiographic techniques (17-19), have been reported in the literature as indicative of patellar malalignment. However, using these preoperative indicators of patellar malalignment, success after lateral release has been, at best, inconsistent. In 1986, Schutzer et al. (20) described the use of midpatellar, lO-20”, knee-flexed computed tomography (CT) scanning to accurately document patellar (mal)alignment. They stressed that the CT scan be imaged through the midpatellofemoral joint because this is the area of articular cartilage force transfer. Three patterns of patellofemoral malalignment were described (Fig. 1). Subluxation is defined as any lateral deviation of the patellar apex from the bisector of the femoral sulcus angle. Tilt is defined by the patellar tilt angle, the angle formed by a line parallel to the lateral facet and the line connecting the posterior femoral condyles, being 7” or less. A combined subluxation and tilt pattern was also described. This study was undertaken to correlate preoperative CT scan data with outcome after lateral release in a group of patients with resistant anterior knee pain. A secondary aim was to investigate what effect degenerative changes in the patellar articular cartilage have on outcome after lateral release in these same patients.
45 PATIENTS 1 - Subluxation
Ll L
FIG. 1. Patellofemoral malalignment patterns in patients with patellofemoral pain as demonstrated by CT scanning. Reprinted with permission (31).
Vol. 8, No. 3, 1992
Twenty patients 16-43 years of age underwent a total of 30 lateral releases for resistant anterior knee pain. All knees were judged clinically to have patellar malalignment. Malalignment was felt to be the cause of the knee pain. The previously described midpatellar CT scans were performed on all knees before surgery. However, the decision to perform lateral release was based strictly on the patient’s symptoms and the clinical impression of patellar malalignment . Arthroscopic evaluation was performed before lateral release. The degeneration of the lateral facet articular cartilage was graded as minimal if it displayed Outerbridge I or II changes or advanced if it displayed Outerbridge III or IV changes (21). The lateral release was then performed through a 2-cm longitudinal incision immediately lateral to the patella. The retinaculum was incised from the fatty plane between the longitudinal fibers of the vastus lateralis and the muscle’s more oblique fibers (22) superiorly and to the tibia1 tubercle inferiorly (Fig. 2). Care was taken not to damage the lateral meniscus. The tourniquet was let down and hemostasis achieved with electrocautery. A complete release was assured if the patella could be everted 90%. Only the skin was closed. Rehabilitation began several days after surgery and continued until full range of motion and adequate muscle strength was achieved. The patients were followed for a minimum of 2 years (range 2-6.25, average 3.75). At the time of last follow-up, patients were rated on a previously used patellofemoral rating scale as good/excellent, fair or poor (Table 1) (20). Any patient requiring further surgery for anterior knee pain was rated poor. Final ratings were then compared with the preoperative CT scan alignment pattern and intraoperative cartilage classification.
M
Type 3 - Tilt without subluxation 19 Patients, 25 Knees
Arthroscopy,
METHODS
RESULTS A complete summary of the data is provided in Table 2. Overall, 50% of the operated knees were rated good/excellent, 27% fair, and 23% poor at the time of last follow-up. Twenty-two knee CT scans displayed excessive patellar tilt with or without patellar subluxation i.e., type II or III in Fulkerson’s (20) classification. No knees with pure subluxation [Fulkerson (20), type I] were in this study. Eight
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RETINACULAR
RELEASE
329
developed reflex sympathetic dystrophy in the postoperative period. Three representative cases, one from each group, will further illustrate the value of preoperative CT scanning and arthroscopy in predicting outcome of lateral release. Case 1 A 21-year-old college student presented with a Syear history of anterior knee pain that was not responsive to conservative measures and was considered for a lateral release. Her preoperative CT scan had a patellar tilt angle of 0” (normal 8’) as
TABLE 1. Patellofemoral joint evaluation scale Points
FIG. 2. The extent of open lateral release used by the authors. The subcutaneous incision extends from the tibia1 tubercle inferiorly through the lateral retinacular fibers and extends into the fatty plane between the vastus lateralis and the more oblique fibers of the vastus lateralis obliquus.
knees had normal CT scans, that is, no lateral patellar tilt or patellar subluxation. The data were than subdivided into three groups according to the CT scan classification (patellar tilt or normal) and the degree of articular cartilage degeneration (minimal or advanced). Group A was composed of 13 knees with CT-documented tilt and minimal articular cartilage changes. Group B was composed of nine knees with CT-documented tilt and advanced articular cartilage changes. Group C was composed of eight knees with a normal CT. This group contained too few knees to further subdivide according to articular cartilage degeneration. Ninety-two percent of group A knees were rated good/excellent and 8% (one patient) rated poor at follow-up. Twenty-two percent of group B knees were rated good/excellent, 33% fair, and 44% poor. Only one patient (13%) from group C was rated good/excellent, with 50% rated fair, and 37% poor at the time of follow-up. Two group C knees (25%)
Limp None Slight/episodic Severe Assistive devices None Cane or brace Unable to bear weight Stair climbing No problem Slight impairment Very slowly One step at a time Unable Crepitation None Annoying Limits activities Severe Instability, “Giving way” Never Occasionally with vigorous activity Frequently with vigorous activities Occasionally with daily activity Frequently with daily activity Every day Swelling None After vigorous activity only After walking or mild activity Constant Pain None Occasionally with vigorous activity Marked with vigorous activity Marked after walking 1 mile or mild/moderate rest pain Marked with walking < 1 mile Constant and severe
5 3 0 5 3 0 20 15 10 5 0 5 3 2 0 20 10 8 5 2 0 10 5 2 0 35 30 20 15 10 0
This patellofemoral rating scale is currently in place at the Department of Orthopaedic Surgery, Division of Sports Medicine, University of Connecticut School of Medicine, Farmington, Connecticut, U.S.A. Total points possible: 100.
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K. P. SHEA AND J. P. FULKERSON TABLE 2. Comparison
between preoperative
Patients
No. of Knees
All Normal CT” CT-documented tilt” Minimal facet changes* Advanced facet changesb
30 8 22 13 9
CT scanning and outcome after lateral release
Average years of age (range)
Average months of follow-up (range)
27 (16-43) 23 (16-33) 24 (lW3)
43 (24-75) 51 (48-75) 40 (24-58)
Excellent/Good 15 1 14 12 2
Fair
Poor
7 4 3 0 3
8 3 5 1 4
D According to Schutzer et al. (20). b See text for explanation.
shown in Fig. 3A. At arthroscopy, the lateral patellar facet was softened, but no breaks in the articular surface were noted (Outerbridge I). Six weeks after lateral release, her postoperative CT scan showed a patellar tilt angle of 17” (Fig. 3B), which is normal. Her knee rated excellent at 3-year follow-up. Case 2 A 20-year-old woman presented with a 7-year history of anterior knee pain that persisted despite activity modification, physical therapy, and bracing. On physical examination, her lateral retinaculum was tender and tight. The patellar tilt angle was - 5” on the preoperative CT scan (Fig. 4A). Arthroscopically, the lateral patellar facet was graded Outerbridge III (advanced changes). Six weeks later, her CT scan showed a patellar tilt angle of 6” (some correction as compared with the preoperative CT
scan, but still abnormal) fair at 4-year follow-up.
(Fig. 4B). She was rated
Case 3 A 20-year-old college student complained of severe anterior knee pain for 1 year. All conservative measures had failed to relieve her symptoms. The preoperative CT scan was normal (Fig. 5A). Arthroscopically , her lateral facet showed minimal changes. The postoperative CT scan was identical to the preoperative scan (Fig. SB). She was rated poor at 2-year follow-up.
DISCUSSION Although there are many causes of anterior knee pain, they can be divided into two main subsets:
3A,B
FIG. 3. A preoperative CT scan (PTA, O”)(A) showing patellar tilt and a postoperative CT scan (PTA, 17”)(B) 5 weeks later showing a normal patellar tilt angle.
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FIG. 4. A preoperative CT scan showing a patellar tilt angle of - 15” (A) and a postoperative CT scan showing a patellar tilt angle of 6” (B). which is clearly improved over A but still abnormal.
those in which the patella is normally aligned, and those in which the patella is malaligned. Patellar malalignment can be further divided into two basic types: those with lateral patellar subluxation, and those with excessive lateral patellar tilt. Schutzer and Fulkerson (20) identified a group in which both malalignment patterns coexist. At this
time, it is unclear whether medial patellar subluxation and/or medial patellar tilt exist other than as complications of surgery. Twenty-two knees in this series had CT scanidentified lateral patellar tilt with or without combined patellar subluxation. The syndrome of excessive lateral patellar pressure (ELPS) was first de-
5. A scan which normal (PTA, W), and a postoperative CT which indicates no change in patellofemoral alignment has taken place (F’TA, 15”).
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scribed by Ficat (23). In this syndrome, the lateral retinaculum becomes excessively tight, resulting in a lateral tilting of the patella. As knee flexion progresses, the patella is forced into a congruent reduction in the femoral trochlea, which then stretches the shortened lateral retinaculum. Pain in the lateral retinaculum results from stretching of this tightened tissue. The tilting of the patella increases the joint reaction force across the lateral facet, which may eventually lead to cartilage breakdown. Fulkerson (24) has demonstrated microscopic neuromata in the lateral retinaculum that presumably result from excessive stretching of the tight tissue. Continued stretching and irritation of the lateral retinaculum creates inflammation, scarring, and contracture of the lateral retinaculum, which increases patellar tilt and further increases contact pressures in the lateral patellar facet. The key to treatment of this early ELPS knee is early lateral retinacular release to relieve excessive pressure on the lateral facet in order to prevent articular cartilage breakdown. Realignment of the patellofemoral joint, before excessive lateral facet breakdown occurs, should restore the patella to normal alignment and give the best chance of an excellent long-term result. This study supports this theory. Lateral retinacular release was performed on 13 knees with minimal articular cartilage changes and preoperative CT scan evidence of lateral patellar tilt; 12 were rated good/excellent at >Zyear follow-up. It is unclear why one patient failed to respond to this treatment. That patient ultimately was rated excellent after a tibia1 tubercle anteriorization procedure, so we presume the degree of articular cartilage injury was more extensive than was recorded at the time of arthroscopy. Based on these results, we endorse lateral retinacular release in the fashion described for any patient with anterior knee pain, excessive lateral patellar tilt on a preoperative scan, and minimal articular cartilage changes (i.e., Outerbridge grade I or II) who have failed conservative treatment (Fig. 3A and B). Once articular cartilage breakdown occurs in ELPS, collapse in the lateral facet occurs. Facet collapse decreases the height of the lateral patella, which reduces strain on the lateral retinaculum. Although the lateral retinaculum may remain tight, pain now begins to emanate directly from the degenerated patella. Whereas lateral retinacular release may provide relief in many of these patients, lateral release frequently fails to restore the patella Arthroscopy,
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to normal alignment because the patella and femoral trochlea are no longer congruent. Progressive degeneration in the lateral patellar facet may occur, and diminishing satisfaction after lateral release may be seen with time. Huberti and Hayes (25) have demonstrated that cadaver knees with extensive involvement of the lateral patellar facet show no changes in patellofemoral contact stress with lateral retinacular release. The results of this study support this theory as well. Only two of nine knees with extensive lateral facet changes were rated good or excellent at a 22year follow-up. In discussing each patient’s postoperative course at the final follow-up evaluation, many initially benefited from the procedure. However, the results deteriorated with time. Based on these results, we still recommend lateral retinacular release selectively in patients with preoperative CT scan-documented patellar tilt and arthroscopic evidence of grade 3 lateral facet changes. The surgeon should caution the patient if extensive damage is seen in the lateral patellar facet results may deteriorate with time (26). Lateral patellar subluxation until recently has been recognized as the cause of a great majority of anterior knee pain in the malaligned patellofemoral joint. Hughston (17), Insall (9), and Merchant (19) all have described radiographic criteria that would identify lateral patellar subluxation and all have recommended patellar realignment as treatment of these conditions. They all emphasize that although the classic patient with subluxation will have episodes of patellar giving-way or frank dislocations, many of these patients do not present with instability symptoms, but with pain after excessive activities. In the current study, there was only one patient in 44 scanned who had an isolated lateral subluxation pattern. Although we felt it was interesting that given so many patients with anterior knee pain, only one with isolated lateral patellar subluxation could be identified, no comment could be made with regard to the results of lateral retinacular release in these patients. The major causes of anterior knee pain with a normally aligned patella are postoperative neuroma, traumatic chondromalacia patella, arthritis, pain after patella fracture, and reflex sympathetic dystrophy, as well as overuse disorders such as Osgood-Schlatters disease and Sinding-LarssonJohanssen syndrome. Many of the soft tissue overuse syndromes will respond to conservative treatment including avoidance of provocative activities,
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RETINACULAR
rest, and physical therapy. The common thread among the others (i.e., traumatic chondromalacia, idiopathic chondromalacia, and arthritis) is global destruction of the articular cartilage of the patella. There is no one area of focal stress overload in these disorders. The etiology of the pain in these disorders is unknown, but pain is presumed to emanate from the patella itself. Identification of patients with these normal alignment patellar disorders is frequently difficult. Most will have a typical onset of blunt trauma to the anterior knee and a prolonged course of knee pain that has been unresponsive to all other forms of treatment. Many of these patients will be workers’ compensation patients or involved in litigation after motor vehicular accidents, which will further cloud the issue. When conservative management fails, lateral release has been entertained as a possible treatment for relief of pain. However, because there is no focal stress overload in the patellofemoral joint, lateral release will uniformly fail. Huberti and Hayes (27) have demonstrated in a cadaver model that knees with presumably normal patellofemoral alignment do not undergo any stress alterations in the patellofemoral joint with lateral retinacular release. The data in this study support these conclusions. Of the eight patients with long-standing anterior knee pain that was not responsive to conservative treatment, seven patients either failed to improve or became worse after lateral retinacular release. This was true regardless of the severity of articular cartilage degeneration in the patella. Nine other patients with anterior knee pain and normal midpatellar transverse CT scans were seen during the study, but were not offered lateral release (28). When these patients were contacted later, they all had received lateral retinacular release at other institutions. All nine of these patients were also rated as having a poor long-term result on the patellofemoral rating scale. Therefore, we do not recommend lateral release in patients with anterior knee pain but a normally aligned patella. This study emphasizes the importance of preoperative CT scan in selecting those patients who are most likely to improve with lateral retinacular release. However, we do not recommend a patellofemoral CT scan on every patient with anterior knee pain. Instead, we recommend that a CT scan be performed only after the patient has failed what the surgeon believes is an extensive conservative treatment program and is considering surgical treatment. Midpatellofemoral CT scans (29) are then ordered
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and only those patients with documented malalignment are offered realignment surgery. This study does not support any one treatment for the painful but normally aligned patella. Instead, it only offers experiential evidence that lateral retinacular release performed without preoperative tilt will not relieve pain in many cases. In fact, several of the patients were made worse by this procedure. SUMMARY In summary, the current study demonstrates that the use of preoperative CT scanning is essential to identify whether patellar malalignment exists before surgical lateral release. In those patients with CTdocumented tilt and minimal articular cartilage degeneration as seen at the time of surgery, lateral retinacular release was shown to produce >90% good or excellent results at >2-year follow-up. In those patients with CT-documented tilt and extensive lateral facet changes, the long-term results of lateral release were not as good, but we still recommend the procedure as a first-line attempt to relieve patellofemoral pain in selected patients. In those patients with a normally aligned patella on the preoperative CT scan, we do not recommend lateral retinacular release, because little benefit can be expected. Further investigations are needed to identify the optimal procedure for the normally aligned but painful patella and those patients who have extensive lateral facet changes when first seen by their surgeon. REFERENCES 1. Merchant AC, Mercer RL. Lateral release of the patella. Clin Orthop
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19. Merchant AC, Mercer RL, Jacobsen RH, Cool CR. Roentgenographic analysis of patellofemoral congruence. J Bone Joint Surg 1974;56A:l391. 20. Schutzer SF, Ramsby GA, Fulkerson JP. The evaluation of patellofemoral pain using computerized tomography. Clin Orthop 1986;204:286-93. 21. Outerbridge RE. The etiology of chondromalacia patellae. J Bone Joint Surg 1961;43B:752-7. 22. Hallisey M, Doherty N, Bennett W, Fulkerson J. Anatomy of the junction of the vastus lateralis tendon and the patella. J Bone Joint Surg 1987;69A:545. 23. Ficat C, Bailleux A. Syndrome d’hyperpression externe de la rotale (SHPE). Rev Chir Orrhop 1975;61:139-59. 24. Fulkerson JP, Tennant R, Jaivin J, Grunnet M. Histologic evidence of retinacular nerve injury associated with patellofemoral malalignment. C/in Orthop 1985;187: 196-205. 25. Huberti H, Hayes W. Patellofemoral contact pressures. J Bone Joint Surg 1985;66A:715-24. 26. Fulkerson J. Anteromedialization of the tibia1 tuberosity for patellofemoral malalignment. C/in Orthop 1983;177: 176-81. 27. Huberti H, Hayes W. Contact pressures in chondromalacia patellae and the effects of capsular reconstructive procedures. J Orthop Res 1988;6:499-508. 28. Bernstein R, Fulkerson JP. Unpublished data. 29. Fulkerson J, Hungerford D. Disorders of the patellofemoral joint. Baltimore, Maryland: Williams & Wilkins, 1990.
