Osteochondral Mosaicplasty

The Ghent Experience

K.F. Almqvist, M.D., P. Verdonk, M.D., P. Van Overschelde, M.D., S. Desmyter, M.D., R. Verdonk, M.D., Ph.D.

Department of Orthopedic Surgery and Physical Medicine

Ghent University Hospital

De Pintelaan 185

B-9000 Gent

Belgium

Introduction

Mature articular cartilage has virtually no intrinsic repair capacity (1,2). However, if the damage extends into the subchondral bone, there is repair with fibrous tissue which may undergo metaplasia to form fibrocartilage containing mainly collagen type I (3). Traumatic osteochondral and chondral lesions, osteonecrosis, osteochondritis dissecans and osteoarthritis have in the past been treated by lavage (4), abrasion techniques (5), microfracture (6), perichondrial and periosteal grafts (7,8) slurry grafting (9) and corrective osteotomy (10,11). None of these techniques provide a neochondrogenesis and the defects are progressively replaced by fibrocartilaginous tissue (3,12). This repair tissue is micro-anatomically and functionally inferior to normal hyaline cartilage and ultimately results in degenerative changes while individuals are still young. Recently two techniques with more promising short-term results have been reported: autogenous chondrocyte implantation (13) and mosaicplasty with osteochondral plugs (14). Osteochondral allo- or autografting has been used for osteochondral defects since Lexer introduced the use of allografts in 1908 (15). Since then osteochondral allografts have become a common practice. We present our short-term results of allogenic viable fresh osteochondral mosaicplasty for (osteo)chondral defects.

Materials and Methods

Donors and in vitro culture of the grafts

Donors were obtained by the Ghent Organ Retrieval Program. Femoral hemicondyles were harvested under strictly aseptic conditions in the operating theatre, maximally 12 hours after life support had been terminated. All criteria for organ retrieval as set by the American Association of Tissue Banking were met (16).

The allografts were placed in Dulbeccoís modified Eagleís medium (DMEM) supplemented with 20% serum from the recipient, 0.002M L-Glutamine and antibiotics and antimycotics (penicillin 10 U/ml; streptomycin 10 (g/ml; fungizone 0.025 mg/ml). The allografts were stored in an incubation chamber at 37∞C and 5% CO2. The incubation medium was replaced twice a week (17).

After a two-week period in in vitro culture the femoral hemicondyle was taken to the operating room. The osteochondral grafts were harvested manually with tubular cutting chisels (Arthrex). With fresh osteochondral allografts from femoral hemicondyles for mosaicplasty an identical anatomical form and curvature of the articular surface of the graft can be obtained.

Patient population

Seven patients, 3 females and 4 males, were operated on their knees. The mean age at operation was 29.4 years (16-38 years). The lesions were osteochondral and involved the weight-bearing portion of the lateral femoral condyle in 5 patients, the medial femoral condyle in 1 patient and the lateral tibial plateau in 1 patient. Two lesions were post-traumatic (1 situated at the lateral femoral condyle and 1 at the lateral tibial plateau) and 5 lesions were due to osteochondritis dissecans. The treatment of 1 lesion at the lateral femur was combined with allogenic, fresh viable lateral meniscal transplantation (17,18). At operation the knees showed no degenerative changes, neither macroscopically nor radiographically.

A questionnaire distributed by the"SociÈtÈ FranÁaise d'Arthroscopie" was preoperatively completed: the patients were asked if the injured knee influenced their functional performance. The injured knee was also subjectively compared to the unaffected knee (table 1). A Visual Analogue Scale (VAS) ranging from 0 to 10 and an International Knee Documentation Committee-score (IKDC-score) were determinated. The morphotype (valgus or varus alignment, normoaxial) of the knee was noted.

Twelve months postoperatively the patients were reevaluated with the use of the above-mentioned questionnaire, the VAS and IKDC-score.

Operative technique

The surgical procedure was designed to meet the functional needs of each individual patient. A small arthrotomy of the knee was performed. At the recipient site holes were drilled manually, perpendicular to the articular surface, down to the subchondral bone with specially designed tubular cutting chisels (Arthrex). Care was taken to obtain a good bed of bleeding subchondral bone for the harvested allograft to be implanted. Once proper depth was achieved the chisel was toggled, breaking the graft off at the top. The holes were made 1-2 mm deeper than the graft to ensure that the graft was not blocked in the depth. The graft was secured by press fit. A plastic impactor was used to set the grafts flush with the surrounding articular surface. Hemostasis was performed and the wound was closed in layers. CPM was started immediately postoperatively. The patients were instructed not to bear weight for 3 to 4 weeks. They were encouraged to return to their previous occupations.

Results

The knees all showed a normoaxial morphotype and a grade 4 osteochondral lesion. They were mostly operated on soon after the osteochondral lesion with a mean of 9 months (1 month to 26 years).

All except 2 patients reported a functional improvement of their operated knee. A 37-year-old male patient (patient n∞ 2) with a traumatic lesion at the lateral femoral condyle and a 37-year-old female patient (patient n∞ 6) with osteochondritis dissecans at the medial femoral condyle remained at the same functional level (ìI can do almost everything with my kneeî and ìI am limited in my activitiesî, respectively).

When the patients evaluated their injured knee 12 months postoperatively, all (except patient n∞ 2) reported a better function. However, this patient remained at the same level with a self-evaluated 70-90% function of his operated knee when compared to the non-injured knee.

In all patients the VAS was remarkably better at 12 months postoperatively than it had been preoperatively, as seen in table 2.

The global IKDC-score also showed an improvement at 12 months postoperatively when compared to the global preoperative IKDC-score, except in patient n∞ 2, whose IKDC-score was unchanged (C). All patients returned to the same physical level, except patient n∞ 6 who performed at a lower physical level. There was a 100% return to the previous occupation.

In patient n∞ 6 loosening occured and the osteochondral plugs had to be removed.

Discussion

Large fresh allogenic osteochondral grafts present some immunological problems due to the bony component in human (19,20). This has also been reported in experimental animal studies when a limited area was replaced (21,22). Conversely, an absent or negligible immunological response to allogenic osteochondral grafts has been described (23,24). Cartilage is an immunologically privileged tissue (25), and there is no substantial evidence to suggest that immunological factors lead to rejection or destruction of the graft (26). In our series no clinical signs of immunological reaction or rejection was observed when fresh viable osteochondral allografts were used for treating limited osteochondral lesions. Others have confirmed that the viability of the cartilage is enhanced if fresh instead of frozen allografts are implanted (27). With autografts morbidity has been reported at the donor site (28). This problem is obviated when allografts are used. Another advantage of the allografting of osteochondral plugs from fresh femoral hemicondyles, is that the graft is taken from the same anatomical place as the lesion in the injured knee. Therefore, the form and curvature of the articular surface are practically identical to the articular surface that existed before the knee injury.

Clinically, success can be measured in terms of freedom from pain, swelling, and mechanical symptoms such as locking. Good clinical results were obtained in all patients with a traumatic osteochondral lesion of the weight-bearing portion of the knee and in 4 out of 5 patients with osteochondritis dissecans. Disappointing results have been reported in primary osteoarthritis, probably due to an older patient group with often overweight and associated deformities (27).

Although most authors agree that traumatic osteochondral and osteochondritis dissecans lesions treated with mosaicplasty have the same clinical outcome (29), inferior clinical results have been reported in a small osteochondritis dissecans group (27). In steroid-induced osteonecrosis, osteochondral grafting has also given inferior clinical and histological results (27). The only major complication our patient group was loosening of the osteochondral grafts in a patient with osteochondritis dissecans (pat. n∞ 2).

Trying to match the allograft articular surfaces on both sides of the knee is difficult (27), and leads to stress concentration on the fragments and compression or fragmentation of the bony part of the graft, with subsequent instability, incongruity, or malalignment. It is preferable to place unipolar and unicompartmental grafts, which means that this has to be done before secondary changes occur to the opposing surface.

Meniscal defects or absence should be corrected before or simultaneously with placement of the allograft in order to create the patient a biomechanical environment that would maximize the acceptance and preservation of the allograft.

Our good clinical results with mosaicplasty for osteochondral lesions in the knee are supported by others performing the mosaicplasty with autografts (14). However, we have to keep in mind that these are short-time clinical results, and a final evaluation of osteoarthritis prevention with this technique cand only be made when long-term results are available.

5. Tables

Table 1: Questionnaire

Functional status:

I can do what I want with my knee

I can do almost everything with my knee

I am limited in my daily activities due to my knee

I cannot do anything with my knee due to pain/hydrops

Comparison with healthy, contralateral knee:

Compared with my healthy knee, my lesioned knee functions:

( 90-100% ( 70-90% ( 40-70% 0-40%

Table 2:Visual Analogue Scale

Patient Preoperative Postoperative1 6 02 8 33 6 24 5 05 8 66 6 57 1 0

The VAS of patients who underwent mosaicplasty for an osteochondral lesion at their knee. 0 means no pain and 10 maximal pain.

6. Figures

A 22-year-old male with an osteochondral defect on the medial femoral condyle due to osteochondritis dissecans. A: preoperative MRI; B: postoperative MRI at 6 months.

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