Management of 2 to 3 cm2 Osteochondral Defects of the Knee with Subchondral Drilling in Patients Less than 50 Years of Age

Articular cartilage defects in the knee do not heal and may dispose a predisposition for an early onset of osteoarthritis [1]. Large osteochondral defects are associated with mechanical instability and are accepted indications for surgical intervention to prevent development of degenerative joint disease [2]. The treatment of cartilage defects represents a common, complex and multifaceted task for orthopaedic surgeons; particularly, in young patients suffering from large cartilage defects, there are only limited conservative and surgical treatment options. Thus, several efforts to restore articular cartilage were undertaken. Ideally, a large osteochondral defect should be repaired with a graft that can provide mechanical stability and allow early postoperative function under physiologic loading condition [3]. Disagreement exists for treatment of lesions over 2-3 cm2, while both Osteochondral Cylinder Transplantation (OCT, OATS) or the different modalities of Autologous Chondrocyte Transplantation (ACT) as well as Matrix-Assisted Chondrocyte Transplantation (MACT) techniques are being applied. Furthermore, novel techniques, such as autologous matrix induced chondrogenesis or one-step procedures [4] do or will stand by for execution in the desired patient, while arthroscopic techniques [5] are described with increasing frequency. Cartilage repair is applied with a constantly increasing frequency, while there is both, no internationally accepted algorithm for treatment of cartilage defects or survey to describe how experienced surgeons handle cartilage lesions [6]. No internationally accepted algorithm for treatment of cartilage defects or survey to describe how experienced surgeons handle cartilage lesions. Also, the increased complication rate of autologous or artificial bone graft in management of osteochondral defects of the knee beside lack of experience and also for economic reasons in many places all over the world it was our hypothesis of this study to show that the over drilling is effective, safe method of treatment for knee osteochondral defects among 2-3 cm2. Methods


Introduction
Articular cartilage defects in the knee do not heal and may dispose a predisposition for an early onset of osteoarthritis [1]. Large osteochondral defects are associated with mechanical instability and are accepted indications for surgical intervention to prevent development of degenerative joint disease [2]. The treatment of cartilage defects represents a common, complex and multifaceted task for orthopaedic surgeons; particularly, in young patients suffering from large cartilage defects, there are only limited conservative and surgical treatment options. Thus, several efforts to restore articular cartilage were undertaken. Ideally, a large osteochondral defect should be repaired with a graft that can provide mechanical stability and allow early postoperative function under physiologic loading condition [3]. Disagreement exists for treatment of lesions over 2-3 cm², while both Osteochondral Cylinder Transplantation (OCT, OATS) or the different modalities of Autologous Chondrocyte Transplantation (ACT) as well as Matrix-Assisted Chondrocyte Transplantation (MACT) techniques are being applied. Furthermore, novel techniques, such as autologous matrix induced chondrogenesis or one-step procedures [4] do or will stand by for execution in the desired patient, while arthroscopic techniques [5] are described with increasing frequency. Cartilage repair is applied with a constantly increasing frequency, while there is both, no internationally accepted algorithm for treatment of cartilage defects or survey to describe how experienced surgeons handle cartilage lesions [6]. No internationally accepted algorithm for treatment of cartilage defects or survey to describe how experienced surgeons handle cartilage lesions. Also, the increased complication rate of autologous or artificial bone graft in management of osteochondral defects of the knee beside lack of experience and also for economic reasons in many places all over the world it was our hypothesis of this study to show that the over drilling is effective, safe method of treatment for knee osteochondral defects among 2-3 cm².

Methods
Twenty six patients (18 men and 8 women) with focal full-thickness cartilage lesions of the knee on the medial or lateral femoral condyle, or trochlea were included in this study through the period from 2006-2010. Age of the patients ranged from 23 years to 49 years (mean 36.7 years). All patients were complaining of symptom-like pain or dysfunction of the knee joint. Patients with at least one of the following criteria were excluded from this study: severe osteoarthritis; small lesions <2 cm², age over 50 years, presence of active infection; and limb malalignment and presence of radicular pain. Eighteen patients had previous operations Patients included meniscectomies (in 6 patients) and reconstructions of the anterior cruciate ligament (in 12 patients). Presence and grade of meniscal and cartilage lesions as well as Bone Marrow Edema Pattern (BMEP) were assessed using a modified whole organ MRI score (WORMS) [7]. There were 12 patient's grade 5 and the rest were grade 6.
Lysholm and Gillquist [8] score was used for evaluation of outcome. Clinical evaluation and scoring were done preoperatively and at follow-up. The surgical technique is through subchondral drilling. This technique enhances chondral resurfacing by providing a *Corresponding author: Tarek Aly, Department of Orthopedic Surgery, 48 th , Sarwat street, Tanta 31111, Egypt, Tel: 2040 3317928; E-mail: elphara3on@hotmail.com suitable environment for tissue regeneration and by taking advantage of the body's own healing potential. Multiple perforations into the subchondral bone plate were done. The perforations are made as close together as necessary, but not so close that one breaks into another. Consequently, the drilling holes are approximately three to four millimeters apart (or 3 to 4 holes per square centimeter). Importantly, the integrity of the subchondral bone plate is maintained. The released marrow elements form a "super clot" which provides an enriched environment for tissue regeneration. Postoperatively, CPM was used for all patients from the 2nd day of operation and patients were allowed for partial weight bearing for 6 weeks.

Statistical Analyses
Analyses were performed using Sigma Plot 10.0 and Sigma Stat (SPSS). The level of significance was defined at P=0.05.

Results
The patients had complained of pain for 3-15 months preoperatively. Nineteen of them reported rest pain. Clinical evaluation of the patients revealed Mild knee effusion in 19 patients and moderate in 7, tenderness over the affected area was noted in all patients. Limitation of range of motion of the affected knee was observed in all cases (average flexion: 93.4°, Average extension: -9°).
The mean follow up was 38 months (range 25-54 months). In 17 patients, the lesion sized 2 cm², between 2-3 cm 2 in 3 patients and it was 3 cm² in the rest of the patients. Postoperatively, pain disappeared in 23 patients and was mild in 3 patients. Knee effusion disappeared in all patients. Average range of motion improved to 140° flexion and -0.5 º extensions respectively. Lysholm score was 43.0 ± 12 preoperatively, improved to 88.0 ± 9 postoperatively (P<0.0001). Only 2 patients were complaining of slight impairment of climbing stairs and one patient was complaining of difficulty in squatting.
Radiologically using MRI, complete healing of the defect was observed in all cases (Figures 1-6) except 2 (Both were WORMS's grade 6). No progression of the lesion or development of osteoarthritis was noted tell the end of follow-up period.

Discussion
Treatments for managing articular cartilage defects of the knee are not always effective. When they are, long-term benefits may not be maintained and osteoarthritis may develop. Marrow stimulation techniques such as drilling or micro fracture are first-line treatment options for symptomatic cartilage defects. Common knowledge holds that these treatments do not compromise subsequent cartilage repair procedures with autologous chondrocyte implantation [9].     Autologous osteochondral mosaicplasty may be an alternative for small and medium-sized focal chondral and osteochondral defects of weight bearing surfaces of the knee and other weight bearing synovial joints [10]. There is at present no evidence of significant difference between articular cartilage implantation and other interventions [11]. Autologous osteochondral transplant systems have shown encouraging results but there are still problems. Graft matching and contouring to the recipient articular surface is difficult. Donor sites can be a limiting factor. Furthermore, the fibro cartilaginous interface between the donor and recipient site may contribute to breakdown in the long run. Also, the technique is expensive and is technically difficult to perform [12]. Long-term functional outcome is still a significant question mark. In addition, it has not been shown that autologous chondrocyte implantation can prevent degenerative changes. It was previously mentioned that marrow-stimulation techniques such as drilling, micro fracture, or abrasion arthroplasty fail to yield long-term solutions because they typically promote the development of fibrocartilage. Fibrocartilage lacks the durability and many of the mechanical properties of the hyaline cartilage that normally covers articular surfaces [13]. Experimentally, it was proven that subchondral drilling had increased fibro cartilaginous healing with time, with a slight increase in degenerative changes. Drilling may result in a longer-lived repair than abrasion arthroplasty in the treatment of full-thickness lesions [14]. Recent systematic review comparing Micro fracture technique with chondrocyte implantation (ACI) and osteochondral autograft transfer demonstrated no clear superiority of ACI over micro fracture in line with the findings published by other authors [15][16][17]. Micro fracture technique can be done arthroscopically with faster recovery after surgery and with better cosmetical results. Autologous Chondrocyte Implantation (ACI) involves an open technique with inherent disadvantages such as adhesions and prolonged recovery [18] the size and localization of the defect can be assessed by MRI. It also helps in detection of any other intra-articular lesions [19]. Drilling via intraarticular approach has been performed in the past with poor results [20]. This may be due to open surgery techniques with its associated complications. Patients of this study showed highly significant increases in the respective scores used for outcome measurement demonstrating major improvements in activities of daily living and ability to work. None of our patients complained of knee pain after surgery. Mobilization of the affected knee could be started immediately. Our present results are in line with the available literature. Forst et al. [21] reported on the results of core decompression with resolution of pain in 94% of patients when followed for a mean of 35.4 months. Mont et al. found good or excellent results in 73% of patients at mean follow-ups of 11 years [22]. Marulanda et al. [23] avoided progression to TKA in 97% of patients at a mean follow-up of 3 years treated with percutaneous drilling. Bouwmeester et al. [24] concluded that at 10 years follow-up no difference was observed between debridement and drilling and perichondrium transplantation for treatment of an isolated cartilage defect. Imade et al. [25] also had the same conclusion where they stated that no differences in clinical scores were found in patients with a concomitant ACL rupture and an osteochondral lesion treated by drilling or autologous osteochondral grafting at a minimum follow-up of 1year, regardless of the differences at arthroscopic grading [25]. Size of the lesion in the cartilage is also important in deciding the method of management. Profeen et al. [26] in their review of the regenerative treatment options in management of cartilage lesions stated that although evidence-based studies comparing microfracture and ACI have not found significant differences in the clinical outcome, the literature does show that choosing the treatment based on the size and characteristics of the osteochondral lesion might be beneficial. The American Association of Orthopedic Surgeons suggests that contained lesions <4 cm 2 should be treated by microfracture, lesions bigger than that by autologous chondrocyte implantation [26]. In comparing our techniques with other techniques: Attmanspacher et al. [27] studied the outcomes in 18 patients after arthroscopically placed osteochondral autograft transfers for a variety of underlying disorders including osteonecrosis, osteochondrosis dissecans, and osteochondral defects secondary to instability in anterior cruciate ligament-deWcient knees. Short-term outcomes were very good with an average Lysholm score of 90 points (range 78-92 points), suggesting that this procedure is an effective treatment for focal chondral and osteochondral defects [27]. Despite the overall good results in this study, the small number of patients is still a limitation. Larger number with longer follow up period is needed to prove the long term efficacy of this technique.

Conclusion
Subchondral drilling can be an effective approach for the treatment of osteochondral defects sized 2-3 cm². Using this method, most patients who failed non-operative treatment successfully avoided the need for joint arthroplasty after a single joint preserving surgical procedure.