Hypothesis: It is hypothesized that autologous hamstring resurfacing arthroplasty will result in improved functional outcome scores (Oxford knee score) in patients with symptomatic cartilage lesions at a minimum two-year follow-up.

Background: 
The natural history of cartilage injuries and early arthritis is not well understood, and the optimal treatment for cartilage lesions has not yet been established.  Intact hyaline articular cartilage is necessary for normal knee function.  Localized cartilage defects are frequently associated with joint pain, reduced function, and a predisposition to the development of osteoarthritis.  Because articular cartilage has a limited intrinsic healing capacity, cartilage lesions persist indefinitely, and typically progress to global joint degeneration.
To date, no study has analyzed the effectiveness of autologous hamstring resurfacing arthroplasty in the reconstruction of symptomatic cartilage defects.  I wish to test the hypothesis that autologous hamstring resurfacing arthroplasty will result in improved functional outcome scores (Oxford knee score) in patients with symptomatic cartilage lesions at a minimum two-year follow-up.

Background for Defining Optimal Patient Population and Inclusion Criteria:

One of the greatest challenges in Orthopaedics today is how to manage the middle aged patient with symptomatic full thickness chondral injuries and early arthritis of the medial femoral condyle.  It has been demonstrated in two NEJM reports (1,2) that simple knee arthroscopy is ineffective for knee arthritis.  Where as knee replacement is the gold standard treatment in knee arthritis in patients greater than age 60 years, its application in patients younger than 60 years of age remains a matter of debate.  To quote a JBJS paper (1) on this subject, "We consider arthroplasty ..... to be effective operative treatment with durable results for osteoarthrosis in younger patients when other, less invasive measures have failed." (1)  The point here is that knee replacement should not be the first surgical option in patients less than age 60, but rather, other less invasive measures should be tried first.  Hence for patients less than 60 years of age with significant chondral damage there is a substantial need for an alternative procedure that is more than a knee arthroscopy but less than metalic resurfacing.  It is in this patient population that there is the most potential benefit for autologous hamstring resurfacing arthroplasty.

This autologous hamstring resurfacing arthroplasty study will follow some of the general research protocol concepts included in a recent JBJS study on microfracture in knees (4). In this report, the authors performed microfracture in symptomatic, focal high-grade chondral lesions of the weight-bearing femoral condyles, trochlea, and patella in active patients.  The lesions were located on the medial femoral condyle (54%), lateral femoral condyle (23%), and trochlea (23%).  Defect sizes of were up to 1000 mm² in 17% of patients, but ranged up to 2000 mm².
The authors noted that gender, defect size, defect location, defect type, prior operations, and presence or absence of concomitant partial meniscectomy did not appear to influence outcome scores.

Specific Inclusion Criteria:

Failure of non operative treatment.  All patients will receive nonsteroidal antiflammatories, steroid injections, and hyalauronic injections, unless specifically contraindicated.  Specific clinical indicators of chondral lesions will often include activity-related pain, swelling, locking, and, in particular, catching.

Chondral and Osteochondral defects upto 20 cm2.
Ages: 21 to 60 years of age.
BMI of less than 35.

Exclusion Criteria:

Patient age of more than sixty years.
Fixed flexion deformity.
Signficant ligamentous instability.
Generalized tricompartmental osteoarthritis.
Concomitant ligamentous stabilizations.
Limited patient compliance
Patellar maltracking or instability for patellofemoral lesions
High-grade ligament instability (surgical stabilization required for translation of >10 mm to limit postoperative shear forces on the repair cartilage tissue)
Tumor
Infection
Body-mass index of >35.   In the study by Kai Mithoefer (4),  poor results correlated with patients with a lower body-mass index.  The authors felt that excessive loading may be detrimental for articular cartilage repair with marrow-stimulation techniques.

1) A Randomized Trial of Arthroscopic Surgery for Osteoarthritis of the Knee.  NEJM. Volume 359:1097-1107 Sept 11, 2008. Alexandra Kirkley, M.D., Trevor B. Birmingham, Ph.D., Robert B. Litchfield, M.D., J. Robert Giffin, M.D., Kevin R. Willits, M.D., Cindy J. Wong, M.Sc., Brian G. Feagan, M.D., Allan Donner, Ph.D., Sharon H. Griffin, C.S.S., Linda M. D'Ascanio, B.Sc.N., Janet E. Pope, M.D., and Peter J. Fowler, M.D.