Aust. N.Z. J . Surg. 1993.63.200-202

RECURRENT PATELLA DISLOCATION TREATED BY CLOSED LATERAL RETINACULAR RELEASE

RUSSELL MILLER* AND JOHN BARTLETTt

*Nufield Orthopaedic Centre, Oxford, England und tAustin Hospital, Melbourne, Victoria, Australia

This study describes the results of treating selected patients suffering from recurrent dislocation of the patella, with closed lateral retinacular release. Thirty-nine patients were reviewed after a mean follow-up time of 28 months. Thirty patients were substantially improved by the procedure, two patients had sustained a further dislocation. The major complication - haemarthrosis - occurred in four patients. These results compare favourably with those achieved by major realignment procedures. So lateral retinacular release is an effective treatment for selected patients with recurrent patella dislocation, and it offers distinct advantages over other procedures.

Key words: arthroscopy, knee, lateral retinacular release, patella dislocation.

Introduction Patella maltracking is common and, despite the vast literature devoted to the topic, the optimal treat- ment remains contentious. ' This paper describes the results of treating recurrent dislocation of the patella (RDP) by arthroscopic lateral retinacular re- lease (LRR).

The extensor mechanism is stabilized by forces acting medially , laterally and distally. Patella realignment procedures aim to alter these forces by various combinations of

(i) division of lateral structures; (ii) plication of medial structures; and

(i i i ) transfer of the patellar tendon insertion. Techniques that involve repair of anatomical

structures must be protected by a prolonged period of immobilization. This is inconvenient for the patient and may compromise the articular cartilage which requires joint movement for nutrition. Im- mobilization also leads to further atrophy of the quadriceps mechanism which has a deleterious effect on patella stability.

Lateral retinacular release, when used in isola- tion, requires minimal surgical intervention and does not require immobilization. This represents a sig- nificant advantage over other techniques. Previous studies have achieved satisfactory results by treating patella malalignment with LRR.*-' These studies, however, include patients with a wide spectrum of

Correspondence: R. K . Miller. Nuffield Orthopaedic Centre, Headington, Oxford OX3 7LD. England.

Accepted for publication 23 September 1992

patella maltracking problems (such as subluxation, dislocation, and lateral pressure syndrome). This study looks specifically at a selected group of patients with true RDP, treated with closed LRR.

Materials and methods

SELECTION C K l T E R l A

Lateral release alone is not applicable to all patients with RDP and careful patient selection is required. To be included in the study patients had to meet all of the following criteria: (i) clear clinical history of RDP; ( i i ) patella dislocatable under anaesthesia (Patients with different forms of patella malalign- ment have similar clinical features. If the patella recurrently dislocates this feature should be repro- ducible under anaesthesia. Thus only patients with true RDP were included in this study.); (i i i) failed conservative treatment, consisting of physiothera- py, analgesics and activity restriction, for at least three months; (iv) apprehension test positive on lat- eral displacement of the patella.

Patients were excluded from the study if they had evidence of the following features: (i) generalized ligamentous laxity as defined by Ansell;' ( i i ) habitual dislocation of the patella; (iii) avulsion fracture of the patella; (iv) marked malalignment with a Q angle greater than 20 degrees;x (v) previ- ous knee surgery.

The above selection and exclusion criteria rcflect a deliberate attempt to identify a group of patients with a good prognosis following realignment sur- gery, and to treat this group with a less extensive surgical procedure.

RECURRENT PATELLA DISLOCATION 20 1

PATIENTS

Forty-five patients were included in the study and thirty-nine of these were available for follow-up evaluation. Thirty-four patients were interviewed and physically examined, and five patients from rural areas were evaluated by telephone interview. There were 14 male and 25 female patients; the mean age was 26 years (range 15-46 years). Five patients had a positive family history of patella dis- location and eight patients had bilateral knee symp- toms. The mean duration of follow up was 28 months (range 18-40 months).

All patients had pre-operative radiological examination consisting of antero-posterior, lateral and skyline views of the knee.

Results At follow up the patients’ symptoms were evalu- ated and they were placed in the categories outlined above. The results appear in Table 1. Seventy-seven per cent of patients were substantially improved by the procedure.

Improvement in knee symptoms was paralleled by a positive change in the findings of a physical examination. These are displayed in Table 2. Later- al release did not change the Q angle in any patient.

Associated pathology was identified in 19 patients at arthroscopy: chondmmalacia patellae occurred in 12 patients, lateral subluxation in three patients, patellofemoral osteoarthritis in two patients, a loose body was removed from one patient, and a chondral crack of the medial facet was observed in one patient.

Radiological examination demonstrated abnor- mal findings in three patients: two patients had lat- eral subluxation and one patient had patellofemoral osteoarthritis.

Four patients developed a haemarthrosis; all re- solved satisfactorily with conservative treatment. Two patients re-dislocated during the follow-up period. Two patients underwent further surgery in the form of a Roux Goldthwaite procedure because of persisting symptoms; in this study both these patients were classified as worse although they ulti- mately achieved a good result.

The mean hospital stay was 1.5 days and the mean time until walking unaided was 9 days.

FOLLOW U P

All patients were assessed by one author and their symptom pattern was classified using the following categories: Excellent Asymptomatic, return to full vigorous activity including sport. No further dislocations. Good Occasional symptoms with vigorous activ- ity. No further dislocations. Improved Some persisting symptoms not requir- ing medication or further treatment. No further dislocations. Same No substantial change in symptom pattern. Worse Deterioration in symptom pattern.

Physical examination took particular note of quad- riceps wasting, presence of effusion, patellofemoral crepitus, and the Q angle.

OPERATIVE TECHNIQUE

The procedure was performed under general anaes- thesia, the knee was examined to assess ligamen- tous stability and confirm that the patella could be dislocated.

An exsanguination tourniquet was applied and the knee examined arthroscopically via an an- terolateral portal. A number 11 scalpel blade was then inserted at the lateral border of the patella under vision, and the tendinous insertion of vastus lateralis, including synovium, divided. The ad- equacy of lateral release was confirmed by rotating the patella 90 degrees through its longitudinal axis, so that the lateral border faced anteriorly. If this could not be achieved the dissection was extended proximally and distally.

A suction drain was inserted via the lateral arth- roscopic portal and a pressure dressing was applied. The tourniquet was released, making no specific attempt to secure intra-operative haemostasis. On Day One the drain was removed and the patient mobilized with active knee extension.

Discussion Patella maltracking has diverse clinical manifesta- tions. The various clinical syndromes share a com- mon aetiology , but require different treatment

Table 1. Symptom category at follow up

Category Number

Excellent Good Improved Same Worse

15 I 8 I 2

Table 2. Examination findings prior to surgery and at follow-up examination

Examination finding

Pre-operative Follow-up incidence incidence

Quadriceps wasting 21 8 Effusion I 2 Patellofemoral crepitus 18 12

202 MILLER AND BARTLETT

protocols. Only one previous study has looked spe- cifically at RDP treated by closed LRR.' Other studies examining lateral release have not clearly separated the clinical groups, making assessment of the technique more difficult. The present study con- siders a single category of maltracking - recurrent patella dislocation.

LRR aims to restore patella stability by altering only one of the forces acting on the patella. It is not suitable for all patients with RDP and specific selection criteria were used to define the treatment group. The Q angle is a particularly important determinant for choosing patients for this pro- cedure. Patients with a Q angle greater than 20 degrees were specifically excluded from this study; in these patients the oblique pull of the patella ten- don creates a large lateral force on the patella which can only be adequately addressed by distal transfer.

In this series, 77% of patients were substantially improved by LRR; this is comparable to results achieved with major realignment procedures. ''*I1 Dandy and Griffiths treated a series of 41 patients suffering from RDP and LRR and, achieved 90% good or excellent results.' However, their re- dislocation rate (32%) was much higher than the 5% reported in this series. Different selection cri- teria, particularly the exclusion of patients with high Q angles, may account for this difference.

Arthroscopy performed at the time of LRR proved a valuable adjunct, additional pathology was identified in nearly half the patients. This allowed for a more accurate prognosis and the reha- bilitation could be modified according to coexisting pathology. Performing a closed procedure leaves the patient with no visible scar; this is a significant advantage, particularly in young female patients who frequently suffer from this condition.

The major reason for failure in this series was persisting pain. Recurrent dislocation, episodes of giving-way and crepitus all responded well to treat- ment. Haemarthrosis was a troublesome complica- tion in this series affecting nearly 10% of the patients. It did not affect the final result but delayed rehabilitation and return to work.

The superior lateral genicular artery is divided during the procedure and is the likely cause of the haemarthrosis. Other series have performed LRR with electrocautery resulting in a much lower inci- dence of haemarthrosis. The incidence of haemar- throsis may also be reduced by infiltrating the area to be incised with bupivacaine and adrenaline.'

The rehabilitation period following patella realignment surgery has received little attention. In this study the mean period until the patients were walking unaided was only 9 days. This is a major

advantage for the young, active and working popu- lation afflicted by this disease. Two patients in this series subsequently underwent a further operative procedure on the affected knee (Roux Goldthwaite) and both patients ultimately obtained a good re~u1t . I~ Closed LRR does not complicate an open realignment procedure should it be required.

CONCLUSION

Closed LRR is the procedure of choice for appro- priately selected patients suffering from RDP. The results are as good as those achieved with major realignment procedures. The patient enjoys a more rapid rehabilitation and a superior cosmetic result.

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