PURPOSE

Biologic hamstring resurfacing arthroplasty was developed in 2007 as an alternative to total knee arthroplasty in selected patients with end stage arthritis of the knee who were at significantly high risk for infection.  A full description of the background of this procedure and the similarity of this procedure to the AMIC procedure can be found at www.orthonc.com/doc6.html.  Briefly, there are several companies in Europe that have gained CE approval for porcine and bioabsorable membranes that are designed to be surgically opposed over a microfractured joint surfaces.  The combination of a soft tissue scaffold bonded to a microfractured surface has now become well published and well accepted in peer reviewed literature.  The purpose of this study is to determine the safety and efficacy using of autologous hamstrings as the soft tissue scaffold (instead of an artificial membrane) over a microfractured joint surface.  The use of autologous hamstrings as the soft tissue scaffold avoids FDA issues and may have an additional advantage given the potential for tendon to fibrocartilage metaplasia when subjected to compression. Expected outcomes will include improved function, mobility, reduced pain as well as decreased joint crepitus, swelling, and instability.  The study will follow this cohort of patients over a two year period and will determine patient satisfaction (using the Oxford knee score, http://www.orthopaedicscore.com/scorepages/oxford_knee_score.html), as well as any surgical and medical complications.

Source of Funding:  There are no external funding source for this study. 

Study Design
The study design that was deemed most ethical from the patent's perspective was the case series.  This type of study design is well accepted in the peer reviewed orthopaedic journals, and indeed there was a recent JBJS review article on how to design a case series.  Because
there is no control for allocation of patients to treatment, the orthopaedist and the patient will jointly decide on whether or not the hamstring resurfacing treatment is given. (Kooistra et al, JBJS (Am)  2009;91:21-26. How to Design a Good Case Series)

CRITERIA

The patient selection for this procedure is not a random, but the patients are carefully selected for this procedure only. There is no comparison study available for this specific procedure.  Potential candidates will be similar to joint arthroplasty candidates in that they will have to have failed documented aggressive non operative treatment.  This will typically include use of anti inflammatory medications, intra-articular joint injections, hyalauronic acid injections, and use of walking aids.  Patients will be given the option for standard knee arthroplasty as well as the hamstring resurfacing arthroplasty.  For a patient to be accepted into the trial, the procedure will be first explained in detail, including a detailed understanding of possible complications, risk involved, benefits, and they will understand that their unique identification number will be recorded and used for research purposes.  They will then decide if they want to continue with non operative treatment, proceed with a joint replacement, or proceed with autologous hamstring arthroplasty.

Pre Operative Assessment:
All trial patients will have completed a pre-operative assessment by the operative surgeon. The following elements will be assessed: current functional levels, general health, occupation, functional range of movement, balance/proprioception, gait, mobility, including walking aids, orthoses.

Patient Confidentiality:
As a precautionary measure to ensure patient confidentiality, each patient is assigned a specific identification number. The names and identification numbers were kept separately, so that the analysis of the data was performed without knowledge of the identity of the patients. The risks and benefits of operative treatment will be discussed in detail. All patients in the study provided full verbal and written consent for operative treatment and participation in this study.  A private institutional review board will approve the study.

Elements of the Informed Consent: (see online informed consent)
A dedicated informed consent will be signed by all study patients.
Patients will understand that only CR Wheeless MD will perform the surgery.  They will further understand that this is a new procedure as compared to the traditional joint replacement, and therefore the results will be more unpredictable.  Patients will be given Internet access to web sites that discuss the enhanced microfracture concept with the understanding that this may help in their decision making.  They will be told that should the surgery not meet their clinical needs, that most likely, they could still have a traditional knee replacement.
Possible complications that will be discussed with the patient will include infection, bleeding, nerve damage, deep vein thrombosis pulmonary embolism, persistent / recurrent pain, recurrent symptoms including locking, swelling, instability, failure of tendon healing, persistent / recurrent joint crepitus, and altered sensation in the knee post-operatively.
Further patients will be told that they can opt out from the research study without giving a reason and that this will not affected their medical care.

SURGICAL PROCEDURE

The operative leg is prepped down to the foot in order to allow for the potential harvest of the plantaris tendon.
A standard knee arthroscopy is performed in all cases.  This not only allows facile management of meniscus and lateral compartment pathology, but also allows an assessment of the patellofemoral compartment and the need for plataris tendon harvest if resurfacing in this compartment is deemed necessary.

Arthroscopic preparation of the medial compartment is carried out as would be for a standard microfracture as described by Steadman (Steadman, 2001 and 2002).  Degenerated and detached cartilage is completely removed.  The only difference is that instead of using arthroscopic picks and awls, the dense osteoarthritic bone is prepared with a 2.5 mm drill bit in order to remove sclerotic bone rather than further compact it. (Chen et al 2009).  The arthroscopic instruments are removed.

Standard gracilis, semitendinosis tendon harvest is carried out in the usual fashion, as would be done for an ACL reconstruction.  If the hamstring tendons are of insufficient caliber, or if additional tendon graft is required for the femoral trochlea, then the plantaris tendon is harvested in the usual classic technique.  The tendons are taken to the back table, and the surfaces that are expected to face the outer articular surface and gently marked with a sterile marker, and the inner surfaces (facing the microfractured surface) are gently scraped with a knife inorder to debride the outer tendon sheath layer (removing lubricin on the surface).   The later step is performed because the presence of lubricin is known to prevent integration of the tendon onto the osseous surface (Myron Spector, 2009, personal communication).  The tendons are protected with a moist sponge.

A small arthrotomy is made over the medial femoral condole.  The previous debasement and microfracture is refined if necessary.  The hamstring tendon are draped over the medial femoral condole with the free edge facing posterior and the mid aspect of each tendon opposed just proximal  to the far anterior article edge.  The larger semitendinosis is draped on the outside of the gracilis.   A No 5 fibrowire suture is applied through the mid aspect of the tendons which is then passed through the cortical surface using Biomet rotator cuff trochar needles (suture tunnels) using a horizontal ma tress technique.  This tendon opposition to the arthritic Ossie's surface using a horizontal ma tress technique progresses from the anterior aspect of the medial femoral condole to the posterior condole.  The previous microfracture drill holes facilitate the passage of the trochar needles which exit over the medial edge of the condole or exit through the lateral edge at the intercondylar notch.  Once the tendon edges have almost been reached (2 cm from the tendon edges), the suture ends for each tendon are tied together at a distance of about 1 cm from the tendon edge.  A 2.9 mm drill bit is drilled through the cortical surface at a point 1.5 cm from the free tendon edges.  A Mitek bioknotless anchor straddles the suture knot, and is driven into the drill hole.  As the anchor is driven deep, the free tendon edges are brought into the drill hole and are firmly secured.  Additional Mitek bioknotless anchors are inserted over the central condole (straddling the horizontal suture) as necessary in order to obtain maximal secure fixation.  Once the fixation is complete, the tendon has the feel of "hard rubber" and will not move to firm side to side pressure with the surgeon's gloved finger.  At this point there are quadrupled semitendinosis and gracilis tendons rigidly opposed to the surface of the prepared medial femoral condole.  A similar technique is used over the femoral trochlea using the plataris tendon if indicated.

REHABILITATION 

Most of the patients are expected to have a short recovery time, 23 hour hospital stay, and almost no formal physical therapy required. Patent's will be instructed on how to move safely and independently with appropriate walking aids, adhering to touch down weight bearing status.  As with classic microfracture protocols, patients will be expected to remain touch down weight bearing for 6 weeks and to use a CPM for at least 8 hours per day.

RESULTS

The patients who had the surgeries will be followed every three months for a period of 24 months.  At each 3 month visit, patients will be given privacy while they fill out Oxford Knee Score score information questionnaire. The Oxford Knee Score has undergone the most thorough assessment of reliability and validity, and is therefore most appropriate for the assessment of outcome after this type of surgery. The individual Oxford knee item scores and the total scores will be compared and analyzed from the initial preoperative visit to the final 2 year follow up.  Patients will be asked if they would have undergone the hamstring resurfacing procedure again under similar circumstances.
Patients that have also undergone plantaris resurfacing of the femoral trochlea (in addition to the medial femoral condole) will receive the same clinical assessment as well as the Oxford Knee Score assessment.  During the two year study period, if any patient decides that the clinical results of the hamstring resurfacing are unacceptable, and therefore decides to undergo a joint replacement, then their lowest Oxford Knee Score will be maintained as their final score.

Statistical Analysis
The significance of the effect of surgery on the preoperative Oxford Knee Score versus the postoperative Oxford Knee Score was assessed with use of the Wilcoxon signed-rank test on subject changes (the postoperative value minus the preoperative value). All statistical testing was two-sided with a significance level of 5%.

Clinical Assessments:
Clinical assessments will be performed preoperatively and at three month intervals postoperatively for at least two years.  Knee range of motion, use of walking aids, use of oral narcotics, and general function will be documented.  In addition after 6 months, patients will be allowed to resume intermittent intra-articular steroid and/or hyalauronic acid injections on request.  These injections will also be documented.

Complications:
Complications such as infection, deep venous thrombosis, pulmonary embolus, as well as, medical complications will be recorded.