Internal fixation of undisplaced lesions of osteochondritis dissecans in the knee

Transcription

1 Internal fixation of undisplaced lesions of osteochondritis dissecans in the knee R. Din, P. Annear, J. Scaddan From Princess Margaret Hospital, Perth, Western Australia A total of 11 patients (12 knees) with stable lesions of osteochondritis dissecans of the knee underwent arthroscopic fixation of the fragments using polylactide bioabsorbable pins. The site of the lesion was the medial femoral condyle in ten knees and the lateral femoral condyle in two. The mean age of the patients was 14.8 years (12 to 16). At a mean follow-up of 32.4 months (13 to 38 months) all fragments had MRI evidence of union. One patient developed early transient synovitis, which resolved with non-steroidal anti-inflammatory medication. All patients returned to sporting activities within eight months of operation and did not require a period of immobilisation. The treatment of symptomatic lesions in osteochondritis dissecans (OCD) of the knee is difficult, particularly in young patients who wish to maintain a high degree of sporting activity. The traditional management requires long periods of rest and the avoidance of sports. 1-4 Early fixation of the osteochondral lesions may allow an earlier return to physical activity. The introduction of biodegradable pins allows stabilisation of the fragment without the need for subsequent removal. 5-8 We describe the results in 12 knees with stable osteochondral lesions treated with early internal fixation using bioabsorbable pins and drilling. Table I. Hughston scoring scale 9 Score Rating Criteria 4 Excellent No limitation of activity 3 Good Mild aching on strenuous activity 2 Fair Mild aching and swelling on strenuous activity 1 Poor Pain and swelling on mild activity Tenderness Loss of 20 of movement 0 cm to 2.5 cm thigh atrophy 0 Failure Pain and swelling on no activity Tenderness Loss of > 20 of movement > 2.5 cm thigh atrophy R. Din, MBChB, FRCSI P. Annear, MBBS, FRACS J. Scaddan, MBBS, FRCS Orthopaedic Department Princess Margaret Hospital, Roberts Road, Subiaco, Perth, Western Australia. Correspondence should be sent to Mr. R. Din; robertdin03@hotmail.com 2006 British Editorial Society of Bone and Joint Surgery doi: / x.88b $2.00 J Bone Joint Surg [Br] 2006;88-B: Received 19 September 2005; Accepted after revision 6 March 2006 Patients and Methods A consecutive series of 11 patients (12 knees) with stable lesions of OCD of the knee were managed with arthroscopic internal fixation by one surgeon (PA). There were nine male patients and two female, with a mean age of 14.8 years (12 to 16). They were followed up for a mean of 32.4 months (13 to 38). The mean duration of symptoms was 5.1 months (2 to 9). All the patients were restricted in their daily activities before operation, with six experiencing pain on activity and five having swelling of the knee following sport. Four patients were unable to run due to pain in the knee. In all patients the symptoms had been present for at least six weeks. In every case the diagnosis of OCD was confirmed by MRI which showed a lesion involving at least 1 cm 3 and surrounded by oedema. The outcome was evaluated by considering the time taken to return to sport, the Hughston Table II. Patients subjective assessment scale Score Patient subjective assessment 1 Much improved 2 Improved 3 No improvement 4 Worse score 9,10 to assess pain and function (Table I), and a simple four-point subjective rating system (Table II). Patients were reviewed two weeks after operation and subsequently at intervals of three months by an independent clinician (Orthopaedic Fellow at Princess Margaret Hospital). Table III lists the location of the lesion, the stability of the fragment and the number of fixation pins used. The arthroscopic grading system according to Guhl 11 is shown in Table IV 900 THE JOURNAL OF BONE AND JOINT SURGERY

2 INTERNAL FIXATION OF UNDISPLACED LESIONS OF OSTEOCHONDRITIS DISSECANS IN THE KNEE 901 Table III. Patient profile and operative procedures Knee Age OCD * site Size of lesion (mm) Arthroscopic grade (Guhl) 10 Anatomy of lesion MRI classification stage Number of pins used 1 15 Medial femoral condyle 20 x 15 x 12 I In situ II 5 Running 2 16 Lateral femoral condyle 22 x 15 x 9 I In situ III 6 Netball 3 12 Lateral femoral condyle 13 x 13 x 13 I In situ II 3 Basketball 4 14 Medial femoral condyle 7 x 32 x 10 II In situ + articular IVa 3 Cricket split 5 15 Medial femoral condyle 16 x 16 x 12 I In situ II 4 Hockey 6 14 Medial femoral condyle 32 x 20 x 9 I In situ II 2 Football 7 14 Medial femoral condyle 20 x 17 x 12 I In situ II 3 Football 8 16 Medial femoral condyle 15 x 19 x 15 II In situ + articular IIVa 5 Football split 9 15 Medial femoral condyle 25 x 20 x 13 I In situ II 2 Football Medial femoral condyle 20 x 30 x 12 I In situ III 6 Football Medial femoral condyle 10 x 25 x 14 I In situ II 4 Basketball Medial femoral condyle 10 x 20 x 14 I In situ II 4 Football * OCD, osteochondral dissecans Sport Table IV. Arthroscopic classification of OCD * (after Guhl 11 ) Arthroscopic appearance Guhl grade Irregularity + softening of cartilage I No fissure, no definable fragment Articular cartilage breached II Not displaceable Definable fragment, displaceable, still attached by cartilage, III i.e. a flap lesion Loose body and defect in articular surface IV * OCD, osteochondral dissecans Table V. MRI classification of juvenile osteochondral dissecans (OCD) MRI appearance Bone signal intensity change Articular cartilage swelling, stable lesion High-signal T 2 at bone fragment interface ± cysts Articular cartilage intact High-signal T 2 Articular cartilage intact, but swelling + thinning High signal bone-fragment interface High signal extending through articular cartilage OCD fragment displaced from subchondral bone Subchondral surface defects Articular cartilage loss and loose body Stage of lesion and the MRI stage for juvenile OCD according to Hughes et al 12 in Table V. Operative technique. Standard anterior portals were used and a diagnostic arthroscopy was performed initially. The defect was assessed with a probe to determine its size and stability. In ten knees the lesion was in situ with the articular cartilage intact, and in two knees it was split adjacent to the lesion. All lesions were drilled into the adjacent subchondral bone to a depth of 25 mm, with a 1.2 mm Kirschner wire (Synthes Australia pty Ltd., Alexandria, Australia), to encourage bleeding at the base of the lesion and healing. The number of holes drilled depended on the size of the I II III IVa IVb lesion (between three and six). The lesion was then pinned in situ with biodegradable poly-l-lactide pins (Intra Fix Smart Nails; Conmed-Linvatec, Tampere, Finland). 13 A mean of 3.9 (2 to 6) pins were used for each lesion according to its size and were placed in diverging directions for greater compression and stability. There were no intra-operative complications related to the insertion of the pins. Patients were encouraged to start mobilising the knee and to perform quadriceps exercises immediately after the operation. Partial weight-bearing with crutches was advised for four weeks after operation, followed by full weight-bearing. A return to non-contact sports was permitted after three months. At the final follow-up the knees were examined for range of movement, an effusion and tenderness. MRI was carried out to assess union of the fragment. The patients were asked to provide their own opinion on the function of their knee. Results There were no loose bodies in the joints and no other intraarticular lesion. The mean size of the lesions was mm 2 (169 to 664). MRI confirmed that lesions had united within six months of operation. One patient developed synovitis two weeks post-operatively, which was treated with conservative measures and non-steroidal anti-inflammatory medication. It had resolved by the sixth week. At the final follow-up all patients were satisfied with the results and there was no swelling or restriction in movement of the knee. Based on the criteria of Hughston et al 9 eight knees were graded as excellent and four as good. The pre-operative MRI s for knee number 9 are shown in Figure 1. They illustrate a typical MRI stage 1 lesion. Figure 2 shows the MRI scans at 18 months after operation indicating that the lesion has healed. The polylactide Smart Nails (Conmed-Linvatec) are still visible. A summary of follow-up periods and clinical results is given in Table VI. VOL. 88-B, No. 7, JULY 2006

3 902 R. DIN, P. ANNEAR, J. SCADDAN Fig. 1a Fig. 1b a) Anteroposterior and b) lateral pre-operative MRI scans showing a large osteochondral lesion affecting the medial femoral condyle. There are areas of cystic resorption and chondral oedema with intact articular cartilage. Fig. 2a Fig. 2b a) Anteroposterior and b) lateral MRI scans 18 months after operation; the intensity of the lesion is similar to that of the surrounding normal articular cartilage, consistent with a healed lesion. Discussion The natural history of osteochondritis dissecans included the potential avascularity of the lesion, separation from the subchondral bone and subsequent nonunion of the bony fragment. This may give persistent pain in the knee followed by detachment of the fragment of bone from the femoral condyle and the formation of loose bodies within the knee which may cause locking and degenerative arthritis. 14 THE JOURNAL OF BONE AND JOINT SURGERY

4 INTERNAL FIXATION OF UNDISPLACED LESIONS OF OSTEOCHONDRITIS DISSECANS IN THE KNEE 903 Table VI. Clinical results Knee Time to return to sport (mths) Time of healing on MRI (mths) Subjective rating Hughston rating 9 Complications Much improved 4 None Improved 4 None Much improved 4 None Improved 3 None Improved 3 Synovitis resolved Much improved 4 None Much improved 4 None Much improved 4 None Much improved 4 None Much improved 4 None Improved 3 None Improved 3 None The potential for arthritis is multifactorial and depends on the size of the lesion, its location, associated meniscal damage, the alignment of the knee and the weight of the patient. The clinical outcome is likely to be improved by treatment which aims to heal the lesion before detachment occurs. Many treatments have been tried, including removal of the fragment, curettage of the crater, replacement of the fragment with internal fixation, allograft replacement, autograft replacement and autologous chondrocyte transplantation. The aim is to produce a smooth articular surface. Dervin et al 13 reported on internal fixation of OCD lesions in nine skeletally mature patients using polylactic rods, which resulted in excellent results in eight cases. Matsusue et al 15 treated three cases of displaced OCD lesions with polylactide pins. There have been few reports on the treatment of undisplaced lesions. In our series we obtained excellent or good clinical results according to Hughston s criteria, 9,10 with eight knees graded as excellent and four as good. Internal fixation of undisplaced OCD lesions with multiple Smart Nails (Conmed-Linvatec) significantly improved the symptoms and was well tolerated. Compared to non-operative treatment which requires at least 12 months of non-sporting activity according to Sales de Gauzy et al 1 and Linden, 2 stabilisation of the lesions with Smart Nails (Conmed-Linvatec) allowed an early return to sport in our patients without a period of immobilisation. Bioabsorbable pins have been reported to cause articular damage to the femoral condyle. Friederichs, Greis and Burks 16 described two cases in which poly-l-lactide screw fixation for OCD led to damage to the femoral articular surface, with breakage of the screw. We placed the pins at least 2 mm below the articular surface to avoid protrusion and post-operative abrasion of the articular surface. In addition, Smart Nails (Conmed-Linvatec) have barbs at the end that prevent them backing out. We did not observe breakage or loosening of the nails. Another particular advantage with the use of biodegradable non-metallic implants is the avoidance of artefacts on radiological imaging. Pihlajamaki et al 17 observed ten patients between 30 and 51 months after internal fixation of the medial malleolus with polylactide biodegradable screws. MRI showed a good resolution of the implant. With metallic implants it is impossible to use MRI for evaluation. 18 However, biodegradable implants have been associated with some complications. Lytic lesions in bone and foreign body tissue reactions secondary to degradation of the material have been described These changes have been seen particularly with polyglycolide implants, which degrade within six months in 40% of cases. The polylactide implant used in our study degrades much more slowly, generally by about 18 months and local reaction has been seen infrequently, in 3% to 5% of cases A study by Prokop et al 23 evaluated 36 sheep with osteochondral fractures of the femoral condyle. These were treated with polylactide pins and followed up clinically, radiologically and histologically for three years. No adverse reactions were seen. Our experience of internal fixation of undisplaced osteochondral fragments in OCD in skeletally-immature patients using bioabsorbable Smart Nails gave satisfactory results without immobilisation of the knee. This allowed an early return to sporting activities. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. References 1. Sales de Gauzy J, Mansat C, Darodes PH, Cahuzac JP. Natural course of osteochondritis dissecans in children. J Pediatr Orthop B 1999;8: Linden B. Osteochondritis dissecans of the femoral condyles: a long-term follow-up study. J Bone Joint Surg [Am] 1977;59-A: Jakob RP, Franz T, Gautier E, Mainil-Varlet P. Autologous osteochondral grafting in the knee: indications, results and reflections. Clin Orthop 2002;401: Prakash D, Learmonth D. Natural progression of osteochondral defect in the femoral condyle. Knee 2002;9: Barfod G, Svendsen RN. 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