Functional outcome of medial patella femoral ligament reconstruction: a prospective study of novel hamstring sparing technique without patella anchors

INTRODUCTION

The incidence of primary patellar dislocation is 43 per 1,00,000 people and the recurrence is approximately 40%.¹ Recurrent dislocation results in ongoing restrictions and patient outcomes are poor. The medial patellofemoral ligament (MPFL) is one of the primary stabilizers of the patella. About 94%-100% develops MPFL rupture after patella dislocation.² Other causes are Trochlear dysplasia, increased Q angle, genu valgum, external tibial torsion, paella alta.³ Thus, isolated MPFL reconstruction is the main stay of surgical treatment in recurrent dislocation of patella without any trochlear dysplasia and with normal TT:TG distance.⁴ Most common autografts used for MPFL reconstruction is hamstring graft. Cossey and Paterson introduced a newer method of MPFL reconstruction using medial patellar retinaculum in 2005.⁵

In our study a modified technique using composite graft composed of medial patellar retinaculum and quadriceps were used without drilling the patella. Our objective of the study was to find the functional outcome of MPFL reconstruction using this novel technique. We used Kujala and Lysholm knee score for comparing the preoperative and post operative score.

METHODS

Our study was a unicentric, prospective observational study done in Lourdes Hospital Ernakulam from January 2012 to January 2022.Ethical committee approval sought prior to study from Lourdes Hospital Ethical Committee. The study included 60 patients with recurrent dislocation of patella with isolated MPFL tear. We excluded recurrent dislocation of patella patients with concomitant trochlear dysplasia, patella alta, Q angle of more than 20 degrees, revision surgeries MPFL reconstruction with other ligament surgeries and patient not willing to participate in the study.

Patients with recurrent dislocation of patella were evaluated in OPD clinically with apprehension test, patella glide test, test for ligamentous laxity and measured the Q angle. Then patients were sent for radiographic evaluation with x ray knee anteroposterior, lateral view and skyline view of the patella. MRI with CT cuts of the knee were obtained for assessing the MPFL status, trochlear anatomy, TT:TG distance and other ligament status. Patients with isolated MPFL tear were selected for the study after getting written informed consent. The preoperative Lysholm score, Kujala score were evaluated.

Surgical technique

All patients were given spinal anaesthesia. Patient was positioned supine. The involved lower limb was scrubbed, painted and draped. A diagnostic arthroscopy was done, to assess the patella tracking. A longitudinal incision was put medial to the patella (Figure 1). A composite graft composed of medial patellar retinaculum and quadriceps tendon of dimension 8×1 cm was harvested with no: 10 blade (Figure 1). To the distal end of the graft a whip stitch was put with a no 5 ethibond (Figure 2). The proximal end of the graft was sutured on medial border of patella at junction of lower 2/3rd and upper1/3rd with a no: 5 ethibond (Figure 2). A 1 cm incision is put over the medial epicondyle (Figure 3).

The graft was passed through the second and third layer of retinaculum and pulled out through the second incision. Schottles point was identified using an image intensifier, a guide wire was passed at this point direction medially and upwards at 30-degree angulation (Figure 3). A cortex breaker(6mm) was passed and the graft shuttled through this and fixed with 7×30 mm bio screw. While tightening the knee was positioned in 30-degree flexion. By closing the defect medially, medial plication and VMO advancement can also be achieved. Wound closed with no 2 vicryl and skin with stapler. A diagnostic arthroscopy was performed at the end to confirm the patellar tracking.

Post operatively a knee brace was given and non-weight bearing mobilisation started. First 2 weeks knee bending was gradually increased up to 30 degrees. Up to 1 month knee bending allowed was 90 degree and at 6 weeks 120 degree. Weight bearing ambulation started on day one with knee brace in extension. At 6 weeks VMO strengthening exercises and weight training started. Return to sports was allowed when the thigh circumference comparable to the normal limb, usually at 6 to 9 months. The knee scores were repeated at 6 weeks, 3 months, 6 months and there after yearly. Post operative complications were recorded and followed up regularly.

Statistical analysis

All data were recorded systematically in a data collection form. Quantitative data was expressed in mean and standard deviation. Continuous variables were compared by student’s t test between two parameters, and analysis of variance (ANOVA) test when parameters were more than two.

RESULTS

The longest period of follow up was 12 years and shortest period was 2 years with average period of follow up of 5.8 years. Most of our study population was between age group 21- 30 years (38.3%) youngest was 14 years of age and oldest with 45 years.

The average age of study population was 26.83 +/- 9.127 (Table 1). 65% of our study population was female and rest were males (Figure 4).

The mean preoperative Kujala score was 53.22+/-3.289. The mean preoperative Lysholm score was 59.55+/-3.739. The patient was followed up at 6 weeks, 3 months, 6 months and then yearly. In each study period the scores were assessed. There was a statistically significant improvement in preoperative and post operative Kujala score (p value< 0.05) in each study period (Table 2). There was a significant improvement in preoperative and post operative Lysholm score too in every period of follow-up (Table 3)

We compared the outcome in each age group patients. The age group 21-30 years had statistically significant improvement in Kujala score compared to age group above 40 years (Table 4). Thus, from our study younger age group had better outcome.

Comparing the post operative outcome among patients with and without ligamentous laxity there was no significant association (Table 5). Kujala score is almost same in cases with no ligamentous laxity (39.25±9.745) and with ligamentous laxity (39.50±8.071).

The post operative complications were assessed. In 86.6% patients had no complications, 3 patients developed further subluxation (5%), one developed superficial infection and stiff knee (Table 6). Superficial infection subsided by antibiotic administration. Three patients with subluxation had poor compliance to physiotherapy. All of them were treated conservatively with intense physiotherapy. Patient with stiff knee needed manipulation under anaesthesia and further physiotherapy.

DISCUSSION

Medial patellofemoral reconstruction is the mainstay of surgical treatment of recurrent dislocation of patella.⁶ Isolated MPFL reconstruction is only required if there is normal Q angle, no shallowing of trochlear grove, TT:TG distance is normal. There are many surgical techniques for MPFL reconstruction, most commonly using a hamstring autograft and using fixation device over the patella. Cossey et al and Patterson et al developed a technique of MPFL reconstruction using a composite graft composed of medial patellar retinaculum. The study was conducted in 21 knees and followed up for 2 years. In our study longest period of follow up was 10 years. In our study the mean age was 26.8. Most of the patients were between age group 21-30 years and had a better outcome compared to the older age groups. Hiemstra et al noted that younger age at the time of surgery had a significant post operative outcome.⁷

The post operative knee scores improved in every period of study and was also statistically significant. The improvement in post operative knee scores were comparable to the MPFL reconstruction with hamstring grafts. Bellal et al had similar results with hamstring graft and had similar post operative outcome measures.⁸

Shah et al, conducted a meta-analysis based on the complications and failures associated with MPFL reconstruction.^9,10 In the study they concluded that that the most severe complication of MPFL reconstruction was patella fracture. Since our technique was anchorless patella fixation, this dreaded complication was out of question. Knee stiffness was another complication, but in our study only one patient developed it and managed with intense physiotherapy. Dislocation after the surgery was another complication. In our study subluxation was present in 5% of patients that too managed conservatively.

We compared the outcome of MPFL reconstruction in patients with and without ligamentous laxity and it showed no significant relationship. Thus, this surgical technique can also be used for habitual patella dislocation.

The biomechanical property of hamstring graft was studied by Haupt et al, they noted that a 7 mm hamstring graft had an average tensile strength of 2179.44 N.¹¹ But the native MPFL has a tensile strength of 208 N.^12,13 In our technique we harvested medial patella retinaculum has similar tensile strength of native MPFL.

CONCLUSION

The functional outcome of novel technique of medial patellofemoral reconstruction is comparable with conventional techniques. It has added advantage of medial plication and VMO advancement. In our technique the subluxation rate is low, no incidence of patella fracture as it is an anchorless technique and no donor site morbidity. Since it does not require anchor on the patella it is cost effective also.

Still longer follow-up is required to account for development of patellofemoral osteoarthritis. We excluded patients with trochlear dysplasia who underwent MPFL reconstruction include limitations of our study.

Recommendations

This hamstring sparing, anchorless technique of MPFL reconstruction is easy, has no donor site morbidity and subluxation rate is less.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

REFERENCES

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