Volume 26, Issue 2 , Pages 173-183, February 2010
Cam Impingement of the Posterior Femoral Condyle in Medial Meniscal Tears
Article Outline
Purpose
The aim of this study was to compare the results of meniscal repair of the medial meniscus with or without decompression of the posterior segment of the medial meniscus for the treatment of posteromedial tibiofemoral incongruence at full flexion (PMTFI), which induces deformation of the posterior segment on sagittal magnetic resonance imaging (MRI).
Methods
For more than 2 years, we followed up 27 patients with PMTFI who were classified into the following 2 groups. Group 1 included 8 patients (5 male joints and 3 female joints) with a medial meniscal tear with instability at the site of the tear who underwent meniscal repair. The mean age was 23.6 years. Group 2 included 19 patients (16 male joints and 3 female joints) who had a meniscal tear with instability at the site of the tear and underwent meniscal repair and decompression. The mean age was 26.5 years. In decompression of the posterior segment, redundant bone tissue on the most proximal part of the medial femoral condyle was excised. The patients were assessed by use of the Lysholm score, sagittal MRI at full flexion, and arthroscopic examination.
Results
There were no statistical differences in mean Lysholm score between the 2 groups before surgery, but the mean score in group 2 was significantly higher than that in group 1 after surgery. Meniscal deformation of the posterior segment at full flexion on MRI disappeared in all cases after decompression. On second-look arthroscopy, the rate of complete healing at the site of the tear was 0% in group 1 but 57% in group 2, and it was significantly different between these groups.
Conclusions
The addition of decompression of the posterior segment of the medial meniscus to meniscal repair of knee joints with PMTFI allowed more room for the medial meniscus to accommodate and improved both function of the knee joint and the rate of success of repair of isolated medial meniscal tears in patients who regularly performed full knee flexion.
Level of Evidence
Level III, therapeutic case-control study.
Multiple factors may affect the results of meniscal repair, including the duration from onset to surgery, age at the time of surgery, whether the medial or lateral meniscus is involved, type of meniscal tear, rim width, method of treatment, and presence or absence of treatment for concomitant instability.1, 2 However, the effects of the various causes of isolated meniscal tear on the rate of success of meniscal suture have not yet been examined. Although the causes of isolated medial meniscal tear have been investigated,3, 4 they have yet to be fully elucidated. We have paid particular attention to the posterior open angle (POA) formed by the articular surface of the medial femoral condyle and that of the posterior part of the medial tibial plateau on lateral x-ray films of the knee joint at full flexion (sitting XP) (Fig 1).4 The smaller this angle is, the more likely the posterior segment of the medial meniscus seems to be impinged between the femur and the tibia on deep flexion and will eventually be injured. When the meniscal tear is sutured in such a knee joint, the rate of success may be low in patients who regularly perform full knee flexion, because incongruence remains at full flexion. Therefore, to reduce the risk of failure in meniscal repair, we have performed bone decompression of the posterior segment of the medial meniscus in knee joints with posteromedial tibiofemoral incongruence at full flexion (PMTFI).
Figure 1.
POA on sitting XP. Sitting XP was taken as follows: Each patient maintained a sitting-square position on the radiography table with the weight of his or her buttocks on the heels. An X-ray film cassette was placed vertically between the thighs. X-rays were emitted horizontally from the lateral to the medial side of the knee so that the direction of the X-rays and the axis of the femoral shaft created an angle of about 97° posteriorly. The angle formed by the maximum gradient tangent of the medial femoral condyle (L1) and the maximum gradient tangent of the medial tibial plateau (L2) was assumed to be the POA (θ). When the angle opened posteriorly to the knee joint, it was considered positive; when it opened anteriorly, it was considered negative.
The purpose of this study was to compare the results of meniscal repair of the medial meniscus with or without bone decompression of the posterior segment of the medial meniscus. Our hypothesis was that decompression of the posterior segment would reduce excessive stress on the posterior segment of the medial meniscus and improve both function of the knee joint and the rate of success of repair of an isolated medial meniscal tear in patients who regularly performed full knee flexion and had knees with small POAs.
Methods
PMTFI is defined as impingement on the medial meniscus at full flexion in knee joints without instability or osteoarthritic change. Such incongruence induces primarily deformation of the posterior segment of the medial meniscus, as can be seen on sagittal magnetic resonance imaging (MRI) at full flexion of the knee joint (sitting MRI) (Fig 2). Deformation of the posterior segment of the medial meniscus is diagnosed when this portion is not imaged as a triangle on sitting MRI; it is often seen as a quadrangle resulting from the formation of a hump close to the free edge on the femoral side of the medial meniscus (Fig 3).
Figure 2.
Sagittal MRI was performed at full flexion of the knee joint (sitting MRI). The knee joint to be examined was fully flexed and the patient sat square on the heel while the other knee joint was extended with a cushion placed under the buttock. The patient's back was reclined on a backrest so that he or she could be slid into the gantry.
Figure 3.
Sagittal MRI scans showing PMTFI of knee joint: posterior segment on extension (left), posterior segment on full flexion (middle), and middle segment on full flexion (right). (A) In a knee joint without PMTFI, there is no deformation of the middle or posterior segment of the medial meniscus on full flexion. (B) In some cases of PMTFI, only the posterior segment of the medial meniscus is deformed on full flexion. (C) In some cases of PMTFI, the middle and posterior segments are deformed and dislocated anteriorly on full flexion. The lines show the maximum gradient tangent of bone contour of the medial femoral and tibial condyles. The angle formed by the 2 tangents is usually larger than the POA, which is measured on lateral X-ray films of the knee joint at full flexion (Fig 1).
Surgical Technique
The surgical technique of arthroscopic medial meniscal repair (inside-out technique) was essentially that described by Henning and colleagues.1, 5 Para-meniscal tissue at the site of the tear was meticulously abraded by rasping to encourage vascular supply. We used single vertical sutures for patients who had a longitudinal tear confined to the tibial side and stacked vertical sutures for patients who had a bucket-handle tear. Multiple nonabsorbable sutures were placed at 5-mm intervals to fix the torn meniscus firmly to the capsule. Decompression of the posterior segment of the medial meniscus was performed as follows. We first determined the range of bone resection using MRI. The shape of the posterior segment of the medial meniscus, which was not deformed, was copied from the sagittal MRI scan of the extended knee joint. The shape was then pasted onto the normal position of the posterior segment on sitting MRI. Thereafter, the range of resection of the most posterior part of the medial femoral condyle was determined so that the pasted posterior segment was not compressed by the most posterior part of the medial femoral condyle (Fig 4A). A posterior approach to retrieve and knot the sutures for the meniscal tear was used to perform the bony-plasty decompression. To open the joint, an incision was made along the medial margin of the medial head of the gastrocnemius muscle. The most medial and distal part of the femoral attachment of the medial head of the gastrocnemius muscle was incised about 1 cm to obtain a good view of the most proximal part of the medial femoral condyle. The posterior capsule was incised at the proximal end of the joint cartilage (Fig 4B), and the capsule and soft tissue were reflected after subperiosteal dissection. The redundant bone tissue at the most proximal portion of the medial femoral condyle and the most distal part of the femoral metaphysis, which was determined by use of MRI, was excised with a bur (Fig 4C). A flexible rod template was used to obtain the contour of the medial femoral condyle to metaphysis before decompression. The amount of bone that was excised was then visually confirmed by use of this template during the operation. The capsule and medial head of the gastrocnemius muscle were reattached to the original position (Fig 4D). In some patients the relative contact pressure between the posterior segment of the medial meniscus and medial tibial plateau was measured during the operation with a narrow film sensor (I-Scan; Tekscan, South Boston, MA) to confirm decompression of the posterior segment (Videos 1 and 2, available at www.arthroscopyjournal.org).
Figure 4.
Surgical technique. (A) MRI scan showing determination of the range of bone resection performed so that the posterior segment was not compressed by the most proximal part of the medial femoral condyle. The shape of the posterior segment of the intact medial meniscus was copied from the sagittal MRI scan of the contralateral extended knee joint. The line on the medial femoral condyle shows the expected maximum gradient tangent of bone contour of the medial femoral condyle after bone decompression. (B) Posterior capsule incised at proximal end of joint cartilage (arrow). (C) Approach to redundant bone tissue (black area), which is excised with a bur. (D) Reattachment of capsule to original position by absorbable sutures.
Patient Population
Decompression of the posterior segment was considered to be indicated when the following 5 criteria were met. (1) The POA measured on sitting XP was less than 3° (Fig 1). (2) Deformation of the posterior segment was observed on sitting MRI (Figs 3B and 3C). (3) There was pain and tenderness in the medial joint space, associated with deep flexion of the knee joint, that interfered with sports or occupational or daily activities. (4) Deep bending of the knee joint during sports or occupational or daily activities could not be avoided. (5) Arthroscopic findings showed that it was possible to preserve the medial meniscus.
The subjects of this study, who had a vertical medial meniscal tear in only the red-red or red-white meniscal zone on arthroscopy and met the 5 previously described criteria, comprised the following 2 groups. Group 1 included 8 patients (8 joints) with PMTFI who underwent arthroscopic meniscal repair without decompression of the posterior segment, including 5 men and 3 women, aged 18 to 35 years (mean, 23.6 years), between 1994 and 1998. Their follow-up period was 2.1 to 4.3 years (mean, 2.6 years). They included 1 student, 1 tailor, 1 deliveryman, 2 nurses at nursery schools, and 3 engineers. All patients had a sports-related onset of symptoms on deep flexion of the knee joint. The duration of symptoms was 1 to 8 months (mean, 5.1 months). There were 2 bucket-handle tears and 6 longitudinal tears confined to the tibial side. There were 4 cases with a rim width less than 3 mm and 4 cases with a rim width equal to or greater than 3 mm. All meniscal tears were longer than 20 mm and exhibited marked instability at the site of the tear. Group 2 included 19 patients (19 joints) with PMTFI who underwent arthroscopic meniscal repair and decompression of the posterior segment, including 16 men and 3 women, aged 19 to 45 years (mean, 26.5 years), between 1998 and 2005. Their follow-up period was 2.5 to 5.9 years (mean, 3.8 years). They included 1 plumber, 1 plasterer, 1 policeman, 3 deliverymen, 3 nurses at nursery schools, 3 students, and 7 engineers. Sixteen patients had sports-related onset of symptoms, whereas the others had work-related onset. In all patients the onset of symptoms occurred on deep flexion of the knee joint. The duration of symptoms was 1 to 10 months (mean, 5.7 months). In this group there were 5 bucket-handle tears and 14 longitudinal tears confined to the tibial side. There were 9 cases with a rim width less than 3 mm and 10 cases with a rim width equal to or greater than 3 mm. Marked instability at the site of a meniscal tear longer than 20 mm was observed in 14 patients. In the remaining 5 patients, meniscal tears were 10 to 20 mm and exhibited instability. All patients in groups 1 and 2 exhibited various degrees of anterior displacement or locking of the posterior segment on deep bending of the knee joint on arthroscopy (Video 3, available at www.arthroscopyjournal.org). Patients who had articular, patellar, or lateral compartment pathology; loose bodies; or any other pathology that might independently compromise clinical results were excluded from this study. There were 2 patients who had been enrolled in group 2 and left our hospital for reasons related to their occupation. Because these 2 patients could not be followed up for more than 2 years, they were excluded from this study.
Post-treatment Protocol
In group 1 the knee joint was fixed with a plaster cast for 3 weeks. Partial weight-bearing gait was initiated at 4 weeks and full weight-bearing gait at 8 weeks. Sitting square on the heels was permitted at 3 months and sports activities at 5 months. In group 2 range-of-motion (ROM) exercise was initiated 1 day after surgery. Partial weight-bearing gait was initiated at 1 week and full weight-bearing gait at 2 weeks. Sitting square on the heels was permitted at 1 month and sports activities at 3 months.
Assessments
In all patients postoperative results were evaluated by the Lysholm knee score,6 POA, and ROM. Level of activity, evaluated with the Tegner-Lysholm rating system6 before symptoms occurred and after surgery, was also examined. In group 2 the amount of resection of cartilage on the most proximal part of the medial femoral condyle was measured during surgery with a ruler as the maximum surface length of the cartilage from the most proximal articular margin on the sagittal plane. Radiographic findings (Kellgren-Lawrence grading system) and complications were also examined. Sitting MRI was performed between 6 and 12 months (mean, 8.3 months) after surgery. Second-look arthroscopy was performed 0.9 to 2.3 years (mean, 1.8 years) after surgery in all patients in group 1 and 1.1 to 3.5 years (mean, 2.3 years) after surgery in 14 of 19 joints in group 2. These 14 joints included 5 bucket-handle tears and 9 partial tears, which were longer than 20 mm. The criteria of Henning and colleagues1 for meniscal healing were used at second-look arthroscopy: complete healing—stable bonding at the repair site without evidence of any residual defect of the surface; incomplete healing—stable bonding at the repair site but with evidence of some partial-thickness defect of the surface; and no healing—no evidence of bonding at the repair site. This study was approved by the institutional review board of the hospital where surgery was performed.
Statistical Analysis
The significance of the differences in mean Lysholm scores before surgery and after surgery in each group was examined by use of the paired t test with a criterion of P < .05. The significance of the differences in mean Lysholm scores and POAs between the 2 groups was determined before and after surgery with the unpaired t test. The significance of differences in mean Lysholm scores after surgery between the subgroups with bucket-handle tear and longitudinal tear confined to the tibial side, between the subgroups with short and long rim width, and between the subgroups with short and long duration of symptoms was determined in each group by use of the unpaired t test. The significance of differences in arthroscopic findings between the 2 groups, between the subgroups with bucket-handle tear and longitudinal tear confined to the tibial side, between the subgroups with short and long rim width, and between the subgroups with short and long duration of symptoms in each group was determined by use of the Mann-Whitney U test. The significance of differences in mean age and duration of symptoms between the 2 groups was determined with the unpaired t test. The significance of differences in the distribution of knee joints by type of tear (bucket handle or partial) and rim width (short or long) between the 2 groups was determined with the Fisher exact test. The significance of differences in mean Lysholm scores after surgery among arthroscopic findings was determined by use of analysis of variance with the Scheffé method.
Results
In group 1 the mean Lysholm score was 63.5 ± 11.1 before surgery and 86.5 ± 7.8 at 2.6 years after surgery (Table 1). The score after surgery was significantly improved (P = .002) compared with the preoperative score. There were no significant differences in mean Lysholm score after surgery between the subgroups with bucket-handle and partial tear or the subgroups with short and long duration of symptoms, but the mean Lysholm score for the subgroup with short rim width was higher than that for the subgroup with long rim width (P = .03) (Table 2, Table 3, Table 4). The Tegner-Lysholm activity scores before symptoms occurred and after surgery were 5.5 and 4.2, respectively. The mean POA before surgery was 0.4° ± 1.4°. All patients were able to sit square on their heels, although pain and locking symptoms on deep flexion of the knee joint recurred in 6 patients at 0.9 to 2.1 years (mean, 1.5 years) after surgery. On arthroscopic examination, complete healing was found in no joints (0%), incomplete healing in 2 joints (25%), and no healing in 6 joints (75%). There were no statistical differences in arthroscopic findings between the subgroups with bucket-handle and partial tear, the subgroups with short and long rim width, or the subgroups with short and long duration of symptoms (Table 2, Table 3, Table 4). In all patients grade 3 signal was observed at the site of the previous suture on MRI. On sitting MRI, deformation of the posterior segment with opening of the tear gap remained in all patients. Of 6 patients who had locking symptoms, 5 eventually required partial meniscectomy.
Table 1. Results in Each Group
| Group 1 | Group 2 | |
|---|---|---|
| Lysholm score | ||
 Before surgery | 63.5±11.1 | 61.4±9.0 |
| After surgery | 86.5±7.8⁎ | 97.1±3.5⁎ |
| Tegner-Lysholm activity score | ||
| Before onset of symptoms | 5.5 | 4.9 |
| After surgery | 4.2 | 4.7 |
| Second-look arthroscopy† | ||
| Complete healing | 0 | 8 |
| Incomplete healing | 2 | 5 |
| No healing | 6 | 1 |
⁎Significant difference between groups (P < .0001). |
†Significant difference between groups (P = .0009). |
Table 2. Results Based on Type of Tear
| Type of Tear | ||||
|---|---|---|---|---|
| Group 1 | Group 2 | |||
| BH | L | BH | L | |
| Lysholm score (after surgery) | 83.5±9.2 | 87.5±8.0 | 97.2±2.6 | 97.1±3.9 |
| Second-look arthroscopy | ||||
| Complete healing | 0 | 0 | 3 | 5 |
| Incomplete healing | 0 | 2 | 2 | 3 |
| No healing | 2 | 4 | 0 | 1 |
Table 3. Results Based on Rim Width
| Rim Width | ||||
|---|---|---|---|---|
| Group 1 | Group 2 | |||
| <3 mm | ≥3 mm | <3 mm | ≥3 mm | |
| Lysholm score (after surgery) | 92.0±4.5⁎ | 81.0±6.4⁎ | 98.0±2.4 | 96.3±4.3 |
| Second-look arthroscopy† | ||||
| Complete healing | 0 | 0 | 6 | 2 |
| Incomplete healing | 2 | 0 | 1 | 4 |
| No healing | 2 | 4 | 0 | 1 |
⁎Significant difference between rim width subgroups in group 1 (P = .03). |
†Significant difference between rim width subgroups in group 2 (P = .03). |
Table 4. Results Based on Duration of Symptoms
| Duration of Symptoms | ||||
|---|---|---|---|---|
| Group 1 | Group 2 | |||
| <5.1 mo | ≥5.1 mo | <5.7 mo | ≥5.7 mo | |
| Lysholm score (after surgery) | 88.0±5.9 | 85.0±10.0 | 97.4±3.5 | 96.8±3.7 |
| Second-look arthroscopy | ||||
| Complete healing | 0 | 0 | 5 | 3 |
| Incomplete healing | 1 | 1 | 1 | 4 |
| No healing | 3 | 3 | 1 | 0 |
In group 2 the length of resection of cartilage was 0 to 3 mm (mean, 1.0 mm). The mean Lysholm score was 61.4 ± 9.0 before surgery and 97.1 ± 3.5 at 3.8 years after surgery (Table 1). The score after surgery was significantly improved (P < .0001). There were no significant differences in mean Lysholm scores after surgery between the subgroups with bucket-handle and partial tear, the subgroups with short and long rim width, or the subgroups with short and long duration of symptoms (Table 2, Table 3, Table 4). The activity scores before symptoms and after surgery were 4.9 and 4.7, respectively. The mean POA before surgery was −0.2° ± 1.6°, whereas that at 3.8 years after surgery was 28.9° ± 5.2°. On arthroscopic examination, complete healing was found in 8 joints (57%), incomplete healing in 5 (36%), and no healing in 1 (7%). There were no statistical differences in arthroscopic findings between the subgroups with bucket-handle and partial tear or the subgroups with short and long duration of symptoms, but arthroscopic findings in the subgroup with short rim width were better than those in the subgroup with long rim width (P = .03) (Table 2, Table 3, Table 4). In group 2 all patients were able to sit square, and none had pain or locking symptoms on sitting square or osteoarthritic changes on radiography during the follow-up period. Of the 19 patients in group 2, 17 had grade 3 signal at the site of the previous suture on MRI. On sitting MRI, deformation of the posterior segment disappeared in all patients. Complications included 4 cases of paresthesia of the infrapatellar region after surgery, but each remitted completely within 4 months with appropriate treatment. There were 2 patients who required 4 to 5 months to sit square on the heels, whereas the others did so within 3 months. In 1 patient hydrops developed when resuming sports activity, although it disappeared within 3 months.
There were no statistical differences in the mean Lysholm score or POA between the 2 groups before surgery. However, the mean Lysholm score and POA in group 2 were both higher than those in group 1 (P < .0001) after surgery. The second-look arthroscopic findings in group 2 were better than those in group 1 (P = .0009). There were no statistical differences in the mean age or duration of symptoms or in the distribution of knee joints by type of tear or rim width between the 2 groups. The mean Lysholm scores after surgery in the complete-healing, incomplete-healing, and no-healing subgroups were 97.3, 95.4, and 84.4, respectively. There were statistical differences between the complete-healing and no-healing subgroups (P < .0001) and between the incomplete-healing and no-healing subgroups (P = .0007).
Discussion
Neither the mechanism nor the cause of isolated medial meniscal tears without a clear history of trauma has been clearly determined. Habata et al.3 reported that patients with an isolated medial meniscal tear but without any clear history of trauma tended to exhibit varus deformity of the knee. They speculated that degeneration of the medial meniscus in the varus knee led to a meniscal tear. Suganuma4 measured the POA formed by the articular surface of the medial femoral and tibial condyles on lateral radiographs of knee joints at full flexion. He speculated that the smaller this angle is, the more likely isolated medial meniscal tears are to occur in the population of individuals whose daily activities include the performance of deep flexion, and that abnormal bone shape at this site, leading to incongruence of the posteromedial tibiofemoral joint, is one of the causes of isolated medial meniscal tears.
In this study we defined PMTFI as deformation of the posterior segment of the medial meniscus observed on sagittal MRI at full flexion of the knee joint with neither instability nor osteoarthritic changes noted. We speculated that the posterior segment of the medial meniscus of knees with PMTFI is subjected to excessive load and is deformed on each deep flexion, leading to degeneration and tearing of the meniscus. We do not know the incidence of this condition in asymptomatic patients, and we do not know whether this condition requires a previous alteration of meniscal ultrastructure. However, it seems clear that not only PMTFI but also frequent deep flexion of a knee joint appears to be necessary for meniscal tearing. PMTFI seems to be caused by an abnormal shape of the bone in the region from the most proximal part of the medial femoral condyle to the posteromedial aspect of the femoral metaphysis. In particular, the most distal part of the metaphysis seems to be hyperplastic posteriorly and presses the posterior segment on full flexion (Fig 3C). On the other hand, there is a small recess between the medial femoral condyle and the metaphysis in normal knee joints, which the posterior segment of the medial meniscus enters on full flexion (Fig 3A). We therefore performed surgery to create a recess and decompress the posterior segment of the medial meniscus (Videos 1 and 2, available at www.arthroscopyjournal.org).
The typical initial symptoms of patients with PMTFI are crepitation and/or pain of the knee joint on deep flexion. In this early stage, there may be no tears of the medial meniscus. When present, tears are often longitudinal and confined to the tibial side of the posterior segment. Locking symptoms not accompanied by deep flexion of the knee joint with PMTFI usually indicate that meniscal tears are advanced, and such tears are usually of the flap or bucket-handle type. For patients who meet the first 3 of our 5 inclusion criteria, we always recommend conservative treatment, such as limitation of deep flexion, regardless of the presence or absence of meniscal tears, because we frequently observe that the symptoms in these patients can be allayed simply by limiting deep flexion. In patients whose symptoms are unrelieved by conservative treatment, surgical treatment is considered if meniscal tears are present. If not, further examination is performed to determine the cause of pain. In patients who will not accept conservative treatment because they cannot avoid deep flexion of the knee joint during sports or occupational or daily activities, we perform decompression of the posterior segment after determining arthroscopically that the medial meniscus can be preserved. We used a criterion of a POA of less than 3° for decompression, because the incidence of isolated medial meniscal tears increases drastically when the POA is less than 3°.4
Because our study took about 11 years, the methods used for and accuracy of diagnosis by MRI of meniscal tears and evaluation of meniscal repair of these tears changed over the course of the study.7, 8, 9 The final diagnosis of meniscal tears and evaluation of their meniscal repair were therefore performed by arthroscopy. MRI was for the most part used to determine both the presence or absence of deformation of the medial meniscus on deep flexion of the knee joint and the resection area for bone decompression. Among studies with arthroscopic control, complete healing after repair of a meniscal tear is found in 73% to 88% of cases.1, 10, 11, 12, 13, 14, 15 Pujol et al.16 reported poor healing of the posterior third of the meniscus and hypothesized that difficulty exists in abrading the posterior segment with anterior approaches. Logan et al.17 reported that medial meniscal repairs were significantly more likely to fail than lateral meniscal repairs. They speculated that differential movement of the menisci with flexion, with more stress placed on the relatively immobile horn of the medial meniscus, could theoretically place more pressure on a medial meniscal repair. Venkatachalam et al.18 reported that isolated atraumatic medial meniscal tears appeared to fare particularly poorly (33% healing) and that they may be better treated by meniscectomy. Cannon and Vittori10 also reported poor results with repair of isolated medial meniscal tears. They speculated that some knees with isolated meniscal tears had biomechanical abnormalities that predisposed patients to tearing of the meniscus. Kurosaka et al.14 reported 13 cases of repeat tears of repaired menisci after arthroscopic confirmation of healing. They speculated that high levels of postoperative activity may cause increased stress at the site of repair and that chronic tears with repetitive reinjury are especially liable to further damage. Asahina et al.12 reported that arthroscopic identification of locking of a torn meniscus has an adverse effect on meniscal healing. They explained that most bucket-handle sites of locked menisci exhibited degenerative change. Meister et al.19 histologically examined the structural differences between torn menisci in anterior cruciate ligament–intact and anterior cruciate ligament–deficient knees and concluded that longitudinal meniscal tears occurring in anterior cruciate ligament–intact knees may result from early degenerative disease processes. They speculated that attempted repair of the diseased tissue may fail to improve long-term preservation of the meniscus. These reports implied that not only degenerative change at sites of tearing, which might be induced by overstress, but also excessive stress on sites of repair after surgery might result in poor results for meniscal repair. However, the excessive stress on repair sites caused by cam impingement of the posterior femoral condyle has never been investigated in evaluation of failed meniscus repair, probably because morphologic variation of the most proximal part of the medial femoral condyle has not been adequately considered.
Compared with previous studies, our overall rate of success in cases with second-look examination was poor (36%), considering that 68% of the cases had an incomplete tear. When tears were longitudinal and confined to the tibial side of the posterior segment, one option was to leave these partial meniscal tears untouched, especially when the anterior cruciate ligament was reconstructed. However, we repaired these partial meniscal tears when there was instability at the tear site, which impairs the healing process. Concerning why the rate of success in group 1 was 0%, we believe that these patients still had PMTFI after surgery. Moreover, they frequently bent their knee joints deeply, which appears to place excessive pressure on the site of repair and eventually induces retearing. The fact that all patients whose meniscal repair exhibited no healing in group 1 had the sudden onset of pain and locking symptoms on deep flexion of the knee joint by 2.1 years after surgery appears to support this explanation. The rate of success in group 2 was 57%, still lower than success rates in previous reports, although the patients in this group did not have PMTFI after surgery. The reason for this poor result appears to be that those meniscal tears not only caused by repetitive impingement but also with a history of repetitive locking on deep flexion of the knee joint may exhibit degenerative change around the site of tearing,12, 14, 19 adversely affecting meniscal healing, even when confined to the tibial side. However, comparison of the 2 groups showed that the addition of decompression of the posterior segment to medial meniscal repair of knee joints with PMTFI resulted in dramatic improvement of the surgical outcome. The rate of complete healing at the site of meniscal repair on second-look arthroscopy increased from 0% to 57%. We suspect that the growth factors20 and stem cells21, 22 consequently produced at sites of decompression as a collateral effect also increased healing response, yielding better results.
It has been reported that the results of meniscal repair depend on various factors.1, 2 Among the factors that might have affected the rate of healing in this study, differences in neither type of meniscal tear nor duration of symptoms affected Lysholm score or second-look findings in either group. Lysholm score in the subgroup with short rim width in group 1 was significantly better than that in the subgroup with long rim width, whereas arthroscopic findings in the subgroup with short rim width in group 2 were significantly better than those in the subgroup with long rim width. As a result, short rim width had a favorable effect on meniscal repair in both groups. However, there were no statistical differences in the mean age or duration of symptoms or in the distribution of knee joints by type of tear or rim width between the 2 groups. Therefore these 4 factors do not appear to have affected the results of statistical analysis of differences between the 2 groups.
The aim of decompression of the posterior segment is to eliminate PMTFI permanently without complications. In the early stage after decompression, there were 4 cases of paresthesia of the infrapatellar region, 1 patient in whom hydrops developed when resuming sports activity, and 2 patients who required 4 to 5 months to sit square on the heels. However, the first 2 types of complications healed completely within 4 months. Tegner activity score after surgery did not return to the level before symptoms developed in either group. The reason for this appears to be that none of the patients in this study participated in competitive sports and they underwent surgery principally to continue their present work, which required deep bending of the knee joints. The mean Lysholm score in group 2 was significantly better than that in group 1 after surgery. On second-look arthroscopy, the rate of stability at the site of the tear was 25% in group 1, whereas in group 2 it was 93%, suggesting that decompression had a favorable effect on obtaining stability at the site of the tear after surgery. Considering the relation between second-look findings and Lysholm score, better Lysholm scores were obtained in patients who had better arthroscopic findings. These 2 factors thus appear to be correlated. Meniscal deformation on sitting MRI disappeared in all patients who underwent decompression, and the mean POA after decompression remained about 30° during the follow-up period. These findings suggest that the addition of decompression to medial meniscal repair of knee joints with PMTFI yielded more room for accommodation of the medial meniscus and improved function of the knee joint in patients who regularly performed full knee flexion.
There are several limitations to this study. First, patients were not randomized, and treatment of the 2 groups did not start at the same time. Second, the number of patients in this study was small. One of the reasons for the small number of patients may be that patients with PMTFI who need to regularly perform full knee flexion tend to exhibit degenerative meniscal tears, and partial meniscectomy is usually indicated for them. We attempted to enroll more patients who met the inclusion criteria in group 1. However, we were unable to do so because, during the course of the study, it became clear that the results in group 1 were poor. Third, when we performed bone decompression, we used MRI to determine the resection area and a template to guide resection during surgery. However, we were unable to determine how accurately the resection was performed during surgery because this method itself is not very accurate. We therefore did not measure the maximum depth of bone resection during surgery because of lack of accuracy. Use of a navigation system with 3-dimensional computed tomography imaging might be a solution to this problem. Fourth, postoperative protocols differed between the 2 groups. We used restrictive rehabilitation in group 1 and accelerated rehabilitation in group 2. We did not use identical postoperative protocols in the 2 groups because we feared that lack of limitation of motion immediately after surgery in group 1 might have resulted in deep flexion of the knee joints, which might impair the process of meniscal healing. In group 2 we used accelerated rehabilitation, because we feared that immobilization for 3 weeks after bone decompression might delay sitting square on the heels and might thus induce bone and soft-tissue formation in the area of decompression and eventually result in recurrence of PMTFI. However, Barber23 and Shelbourne et al.24 reported that they could not show any statistical differences in the results of repair for isolated meniscal tears between restrictive (immobilization for 6 weeks and non–weight bearing for 6 to 12 weeks) and accelerated (immediate ROM exercise and weight bearing) rehabilitation programs. Thus the difference in postoperative treatment between the 2 groups did not appear to have compromised the results of this study. Fifth, the mean Lysholm score in group 2 was significantly better than that in group 1 after surgery. However, among the 19 patients in group 2, there were 5 patients whose meniscal length was 10 to 20 mm, which might have increased the Lysholm score in group 2 after surgery. Sixth, we did not perform second-look arthroscopy for 5 patients in group 2 whose meniscal tears were less than 20 mm. The true rate of success of meniscal suture in group 2 might thus have differed from our finding. However, examination of the difference in results on second-look arthroscopy between groups 1 and 2 showed that all meniscal tears became longer than 20 mm. Thus this lack of second-look arthroscopy in 5 patients does not seem to have compromised the results of statistical analysis of the results of second-look arthroscopy. Seventh, because we were unable to periodically perform sitting MRI of the patients who underwent decompression after surgery, we were unable to determine with precision the changes in the shape and amount of bone resection during the follow-up period. Further follow-up study is thus needed to determine whether this surgery is permanently effective.
Conclusions
The addition of decompression of the posterior segment of the medial meniscus to meniscal repair of knee joints with PMTFI allowed more room for the medial meniscus to accommodate and improve both function of the knee joint and the rate of success of repair of isolated medial meniscal tears in patients who regularly performed full knee flexion.
Supplementary data
Video 1. Before meniscal repair and bone decompression, the relative contact pressure under the posterior segment of the medial meniscus was highest on deep flexion of the knee joint. Both the contact pressure measured with the film sensor and the flexion angle of the knee joint recorded by a video camera were monitored in real time on the display of a computer and recorded simultaneously by use of I-Scan software.
Video 2. After resection of redundant bone tissue at the most proximal portion of the medial femoral condyle and the most distal part of the femoral metaphysis, the relative contact pressure under the posterior segment of the medial meniscus remained low even on deep flexion of the knee joint.
Video 3. A 20-year-old woman visited our hospital because of crepitation and pain on deep flexion of the left knee joint. She had had no problem with her knee joints until she began to work as a nurse at a nursery school, where she needed to bend her knee joints deeply very often. She felt slight crepitation in the knee joint on deep flexion after working as a nurse. On day, she had the sudden onset of symptoms on deep flexion of the knee joint during sports activity. There was a longitudinal tear confined to the tibial side of the posterior segment with instability at the site of the tear. The posterior segment popped out anteriorly only on deep flexion of the knee joint, and it popped back on extension of the knee joint from deep flexion.
Supplementary data.
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Research was performed at Haga Red Cross Hospital, Tochigi, Japan. The authors report no conflict of interest.
Note: To access the videos accompanying this report, visit the February issue of Arthroscopy at www.arthroscopyjournal.org.
PII: S0749-8063(09)00941-4
doi:10.1016/j.arthro.2009.11.002
© 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.
Volume 26, Issue 2 , Pages 173-183, February 2010
