Full thickness cartilage defects of the femoral condyles are frequent, can be highly symptomatic, and pose treatment challenges when encountered in middle-aged patients. A history of biological repair procedures is frequent and patient management is complex in order to delay joint replacement procedures in active patients. Focal metallic resurfacing provides a joint preserving bridging procedure with a clinical exit into primary arthroplasty.

Purpose

The presence of a Hill-Sachs lesion is a major contributor to failure of surgical intervention following anterior shoulder dislocation. The relationship between lesion size, measured on pre-operative MRI, and risk of recurrent instability after surgery has not previously been defined.

Hypothesis: We hypothesized that the size of Hill-Sachs lesions on pre-op MRI would be greater among patients who failed soft tissue stabilization when compared to patients who did not fail. We also hypothesized that the existence of a glenoid lesion would lead to failure with smaller Hill-Sachs lesions.

Purpose: Historically, there have been few surgical options for patients with focal full-thickness cartilage lesions in the knee who have failed or are too advanced in age for biologic resurfacing treatments, yet are also relatively too young or unwilling to undergo conventional total or unicompartmental knee arthroplasty. The UniCAp knee resurfacing arthroplasty provides an option for these patients that is minimally invasive, preserves the menisci and cruciate ligaments, and retains the bony architecture of the knee joint, thereby providing the potential for a rapid recovery to more vigorous activities than might be permitted after conventional knee arthroplasty, while preserving range of motion. The objective of this study was to examine the clinical results of a patient cohort undergoing the UniCAP knee resurfacing in the medial compartment of the knee.

Method: Prospective patients were screened with history and clinical examination, weight-bearing radiographs, and MRI. Patients were offered UniCap knee resurfacing arthroplasty if they had symptomatic full-thickness cartilage lesions in the medial and/or patellofemoral compartments. The cohort included 38 cases in 35 patients who underwent the UniCAP knee resurfacing procedure in the knee with focal medial compartment (with or without patellofemoral) osteoarthritis in the knee joint. In addition, patients were assessed with validated and established outcome scales including the International Knee Documentation Committee Subjective Form, the Knee Injury and Osteoarthritis Outcome Scale, which includes the WOMAC Osteoarthritis Index.

Results: The average age of patients undergoing knee resurfacing was 48.25 years (Range: 23 to 80). There were 24 males and 12 females. Thirty-one patients underwent isolated medial compartment resurfacing and 7 patients received both a medial compartment resurfacing and trochlear resurfacing. Three patients underwent a concomitant ACL reconstruction and 1 patient underwent a concomitant high tibial osteotomy. The mean duration of follow up was 18 months (Range: 12 to 26 months). There was an overall mean improvement from the pre-operative to post-operative scores in the IKDS-SF (P < 0.01), KOOS (all domains, P < 0.01) and WOMAC Index (P < 0.01). There were no major complications such as deep infection, DVT, or implant failure. In addition, there was no evidence of mechanical symptoms/signs or radiographic evidence of loosening at any time point post-operatively.

Conclusion: The short-term results demonstrate that the UniCAP resurfacing arthroplasty in the knee is a viable treatment option for focal full thickness cartilage lesions in the medial compartment of the knee in patients who are no longer candidates for biologic resurfacing procedures and who are also relatively too young or unwilling to undergo conventional total or unicompartmental knee arthroplasty.

Purpose: Osteochondral allograft transplantation for the treatment of osseous defects to the humeral head has recently grown in popularity. Because only a portion of the articulating surface of the humeral head is replaced, conformity of the allograft to the native surface is imperative to restore the natural geometry of the joint. To achieve proper conformity, it is essential that the curvature of the humeral head of the allograft tissue match that of the native tissue. Curvature determination is also important for shoulder replacement procedures. Curvature of the humeral head is difficult to directly measure in allograft specimens. As a result, predictive measurements, such as the maximum length of the humerus are used to predict this curvature. The purpose of this study was to investigate the value of various anthropometric measurements for predicting humeral head curvature. We hypothesized that the maximum length of the humerus would be the most predictive of humeral curvature.

Method: 60 (28 female, 32 male) cadaveric humeri were obtained from the Hamann-Todd Human Osteological Collection. Specimens ranged from 20 to 35 years of age at the time of death (27.9 ± 4.5, mean ± SD). Specimens from this collection include height and weight as collected at the time of death. All specimens were scanned with a 3-dimensional laser scanner (NextEngine, Santa Monica, California, USA). This scanner has been shown to be accurate to within 0.005 inches. Linear measurements (maximum humeral length, epicondylar breadth) were made according to the recording standards for skeletal remains. Both measurements were made by choosing points on the 3-dimensional scan, rather than the traditional osteometric board. Humeral head curvature was determined by a custom computational code to fit a sphere to the articulating surface of the humerus. Data analysis was performed in Minitab (version 13, State College, PA, USA). A linear regression was performed for each predictive measurement. A stepwise linear regression with forward and backward substitution was performed for the most predictive variables from the initial linear regression.

Results: The most predictive factors (R^2 > 0.5) were epicondylar breadth, height, maximum humeral length, and gender. Based on the linear regression coefficients, these four factors (all normalized) were included in a forward and backward stepwise regression (alpha to enter and remove = 0.15). The resulting equation (shown below) had an R^2 values of 0.807. Humeral Diameter = 0.894 + 0.048*(epicondylar breadth) + 0.043*height – 0.020*gender

Conclusion: Of the predicted measurements evaluated, patient height, epicondylar breadth, and gender were most correlated with humeral head curvature. Including these three factors in a linear regression model increased the R2 value to 0.807. If only a single measurement can be used to size the humeral curvature, patient height will give approximately the same accuracy as epicondylar breadth, and can more easily be obtained.

Purpose: We hypothesized that glenohumeral joint stability will decrease with increasingly larger humeral head defects.

Method: Humeral head defects were created in 9 cadaveric shoulders to simulate Hill Sachs defects. Defects represented 1/8, 3/8, 5/8, and 7/8 of the radius of the humeral head. Secondary factors included abduction angles of 45 degrees and 90 degrees, and rotations of 40 degrees internal, neutral, and 40 degrees external. Specimens were tested at each defect size sequentially from smallest to largest and at each of 6 conditions for all abduction and rotation combinations. Using a 6 degree-of-freedom robot, the humeral head was translated at 0.5 mm per second until dislocation in the anteroinferior direction at 45 degrees to the horizontal glenoid axis.

Results: ANOVA demonstrated significant factors of rotation (p< 0.001) and defect size (p< 0.001). In 40 degrees external rotation, there was significant reduction of distance to dislocation compared with neutral and 40 degrees internal rotation (p< 0.001). The 5/8 and 7/8 radius osteotomies demonstrated decreased distance to dislocation compared to the intact state (p< 0.05 and p< 0.001 respectively). There was no difference found between abduction angles. Post hoc analysis determined significant differences for each arm position. There was decreased distance to dislocation at the 5/8 radius osteotomy at 40 degrees external rotation with 90 degrees of abduction (p< 0.05). For the 7/8 radius osteotomy at 90 degrees abduction, there was decrease distance to dislocation for neutral and 40 degrees external rotation (p< 0.001). For the same osteotomy at 45 degrees abduction, there was decreased distance to dislocation at 40 degrees external rotation (p< 0.001). With the humerus internally rotated, there was never a significant change in the distance to dislocation.

Conclusion: Glenohumeral stability decreases at a 5/8 radius defect and was most pronounced in 40 degrees external rotation and at 90 degrees abduction. At a 7/8 radius humeral defect, there was further decrease in stability at both neutral and external rotation. Internal rotation always maintained baseline glenohumeral stability.

Purpose: Tibial slope is an important contributor to sagittal plane stability. Anterior opening wedge high tibial osteotomy (HTO) has received increased attention for sagittal plane correction. A previous study demonstrated that anterior opening wedge HTO induced no increased strain in the ACL [1]. The goal of this present study was to determine the effect of increasing tibial slope on the strains of the major ligamentous restraints of the knee and on the change in position of the tibia in relation to the femur.

Method: Six cadaveric knee specimens were mounted at 15 degrees of flexion in a testing apparatus providing both compressive and anterior loading. Strains were measured in the ACL, PCL, MCL, and LCL for six randomized loading combinations and 3 conditions: intact, after anterior opening wedge HTO with 5mm plate, and 10mm plate. Tibial translation, rotation measurements and tibial slopes were obtained for each test.

Results: ACL strain was significantly associated with the plating intervention (p< 0.001). ACL strain decreased from −0.66 +/− 1.48 at baseline to −7.44 +/− 6.60 with a 5mm anterior opening wedge HTO and −7.99 +/− 6.45 with a 10mm osteotomy. Stepwise regressions yielded no significant effect of compression, anterior loading or osteotomy or combination thereof on PCL, MCL or LCL strain. Tibial slope and external rotation were significantly correlated with the plating intervention (p< 0.001 for both).

Conclusion: Increasing posterior slope via HTO did not increase strain in any of the major ligamentous restraints of the knee. Increasing tibial slope in the setting of a ligamentous deficient knee can be performed to increase stability without fear of submitting ligaments to increased strain.

Purpose: Previous research has reported that increasing the posterior tibial slope through an opening wedge osteotomy results in an anterior shift in the position of the tibia relative to the femur. However, the effect of this on anterior cruciate ligament (ACL) strain remains insufficiently understood. The purpose of this study was to examine the relationship between tibial slope and tibial translation, as well as between tibial slope and ACL strain. It was hypothesized that increasing the posterior tibial slope would result in an increase in anterior tibial translation thereby increasing strain in the ACL.

Methods: Five cadaveric knees were subjected to a randomized experimental design study. One knee was excluded due to failure of a strain gauge during experimentation, resulting in data for four knees. The femoral and tibial portions of the knee were potted with PMMA and fixed using fixation pins. An anterior-based osteotomy was performed with no osteotomy plate present. A strain gauge was then placed in the anteromedial bundle of the ACL. Each knee was mounted at a flexion angle of 15° and loaded with various combinations of A-P loads (18N, 108N, 209N) and axial loads (216N, 418N), according to the study design. Osteotomies of 5mm and 10mm were then performed and measurements of strain and tibial translation were taken after each according to the study design. Tibial slopes were determined through lateral fluoroscopic imaging.

Results: As posterior tibial slope increased, anterior tibial translation increased as anticipated. However, contrary to expectations, as posterior slope increased, ACL strain decreased. One explanation for this result could be that by performing the osteotomy, the insertions sites of the ACL were being moved closer together resulting in increased ACL laxity. At higher slope angles, translation levels off, suggesting constraint of some tissue besides the ACL.

Conclusions: Although increasing the tibial slope through opening wedge osteotomy leads to an anterior tibial translation, there is no increase in strain on the ACL. Further studies are needed to examine the effect of opening wedge osteotomy on other soft tissue restraints of the knee.

Two fixation devices for rotator cuff repair were compared in a sheep model. Surgical transection of the supra-spinatus tendon insertion was repaired using metallic OBL suture anchors or Suretac II anchors. Twelve weeks postoperatively the repair site was assessed using histology, polarized light microscopy and biomechanical testing. No important differences were found between these two repair methods.

The purpose of this study was to compare traditional rotator cuff fixation devices with bioabsorbable press-fit tacks.

Sixteen sheep were assigned to OBL (n=8) or Suretac (n=8) treatment groups. Four sheep shoulder joints were used as unoperated controls. Treated sheep underwent general anesthesia and a lateral arthrotomy using aseptic technique to allow transection of the supraspinatus tendon insertion. The tendon-bone interface was repaired with two fixation devices according to the manufacturer’s directions. After recovery from anesthesia the sheep were maintained in small pens for twelve weeks. After sacrifice, muscle-tendon-bone blocks were prepared for mechanical testing. The specimen underwent a preload of 25N, followed by cyclic loading (10–50N x10), then loading at 480mm/min until failure. The remaining bone-tendon interface was fixed, embedded in plastic and 100μ undecalcified histological sections were cut, polished and stained.

All tendons had healed to the humerus and the repair site was two to three times larger than unoperated controls. There were no significant differences between the two treatment groups with respect to maximum load, modulus, and energy per unit area. Histological analysis is ongoing.

These data suggest that these two fixation methods are functionally equivalent in this model. Press-fit fixation devices do not knot tying and they can be inserted arthroscopically so they are a convenient fixation method.

This study confirms that press fit anchors and metallic anchors with sutures are equivalent for repair of bone-tendon interfaces.

Funding: Smith & Nephew supplied the fixation devices for this project. Thanks to Deb McWade for technical assistance.

Osteochondral autogenous transfer is an accepted treatment for the management of osteochondral defects in the knee. Concerns about donor site morbidity and kissing lesions of the patella lead us to assess the efficacy of filling donor sites with bioabsorbable bone cement in a sheep model. Donor sites were assessed two, eight and sixteen weeks postoperatively using macroscopic scoring, histology and creep indentation testing. At eight and sixteen weeks after graft harvest there were fewer patellar kissing lesions in the treatment group. Control defects had more extrinsic repair whereas cartilage flow was the predominate source of repair tissue in the treated group.

The purpose of this study was to determine if Norian SRS^® bone cement can mitigate donor site morbidity in a model of osteochondral transplantation in the knee.

Ten sheep were assigned to either a control or experimental group. Under general anesthesia and aseptic technique, four donor site defects were created in standardized non-weightbearing regions of the trochlear ridge. These defects measured 4.5 mm in diameter x 10 mm deep. Norian SRS bone cement was used to fill donor site defects up to the level of the tidemark in five experimental sheep. In the control group (n=5), donor sites were left unfilled. One sheep from each group was sacrificed two weeks postoperatively and two sheep from each group were sacrificed at eight and sixteen weeks. Macroscopic scoring, histology and biomechanical creep indentation were used to assess the knee joints.

At eight weeks, treated defects had more filling by facilitating cartilage flow, yielding fewer kissing lesions on the patella. At sixteen weeks, the treated group had more cartilage flow but little extrinsic repair. The control group defects had a more uniform fill with repair tissue and better biomechanical properties but kissing lesions on the patella remained problem.

Short-term results suggest that unfilled donor sites allow better extrinsic repair at the expense of creating kissing lesions. Norian SRS cement reduced kissing lesions on the patella.

Norian SRS was a barrier to extrinsic repair but supported cartilage flow. Cartilage flow in thicker, human cartilage will be greater. It may be possible to support cartilage flow and still allow extrinsic repair by applying Norian SRS up to but not including the tidemark.

Funding: The authors received funding from Synthes, Canada for this project. Thanks to Deb McWade for technical assistance.

Although soft tissue capsulolabral repairs are the mainstay of treatment for recurrent anterior shoulder instability, bone defects are becoming more commonly recognized as additional problems for these patients. Humeral Head defects have been commonly ignored, however, there are a group of patients with failed procedures who have this as their main pathology.

The purpose of this paper is to present a review of patients with large Humeral Head impression defects with a large structural irradiated Allograft.

From April 1995 to January 2001, eighteen patients with recurrent anterior shoulder instability with Large Humeral Head Defects (> 25%) were treated with irradiated humeral allografts. Patients underwent physical and radiographic examination, subjective assessments including VAS scores for pain, instability, and satisfaction and completed a Constant and WOSI scores to determine clinical result. Radiograhic evaluation included standard radiographs and either MR or CT assessment.

Eighteen Patients with an average age of 31.5 (18–52) were reviewed at an average time of fifty months (24–96) following their surgical procedure. There were fourteen male and four female patients each having had an average of 2.1 (1–8) prior operative procedures. All patients had resolution of their instability with no documented recurrences. All patients had severe apprehension preop and this resolved completely in fifteen. Average loss of external rotation was forty degrees preop and improved to ten degrees postop. Two patients had partial collapse of the graft with symptoms of pain in External Rotation requiring screw removal. There were no other complications. Patients improved on WOSI from 1882 to 381 and had an avearage Constant score of eighty-seven postop. Subjectively all patients would have the procedure again and pain improved from 72.5 to 22.5.

There are certain situations where large humeral head defects contribute to the failure of instability repairs and ongoing instability. Allograft reconstruction with matched irradiated grafts is an excellent alternative for eliminating instability.

Funding: Smith and Nephew

To assess the use of autogenous osteochondral graft fixation (mosaicplasty) in unstable osteochondritis dissecans (OCD) lesions (Clanton type 2 and 3) of the knee.

Eleven patients with x-ray and N4R1 confirmed OCD lesion in their femoral condyle, that had remained symptomatic despite adequate conservative treatment, underwent arthroscopic mosaicplasty plug fixation of the lesion. The OCD lesions were all loose at operation and were all fixed rigidly in situ. using a number of autogenous 4. 5min osteochondral plugs harvested from the edge of the trochlear groove. The patients were prospectively assessed both clinically and by MRI scan at 3, 6 and 12 months and then six monthly. Average follow up was 2. 7 years (2 – 4. 1).

Prior to operation all patients had joint effusions and were experiencing pain limiting their activities. By 6 months post-operation the IKDC score had returned to normal in all cases and none of the patients had joint effusions or pain. Serial NHU scans documented healing of the osteochondral plugs and a continuous articular cartilage surface layer in all cases by 9 months.

Using mosaicplasty plug fixation we were able to obtain healing in all 1 1 unstable OCD lesions. The benefits of this technique are the ability to obtain rigid stabilization of the fragment using multiple plugs, stimulation of the subchondral blood supply and autogenous cancellous bone grafting. We conclude that mosaic-plasty plug fixation of unstable OCD lesions in the knee is a good technique and recommend its use.

Eleven patients with an unstable osteochondritis dissecans lesion (OCD) in their femoral condyle underwent in situ arthroscopic osteochondral graft fixation (mosaicplasty) of the lesion using a number of 4. 5min plugs harvested from the trochlear groove. By 6 months follow-up all of the patients were pain free with no joint effusion and by 9 months all had NW evidence of plug healing and continuous articular cartilage coverage. The benefits of this technique are the ability to obtain rigid stabilization, stimulation of the subchondral blood supply and cancellous bone grafting. We conclude that mosaic-plasty fixation of OCD lesions is a useful technique.

Purpose: The objective of the study was to perform a prospective evaluation of thermal capsulorraphy for the treatment of multidirectional instability of the shoulder.

Summary of Methods: Over a period of two years, 19 patients with multidirectional instability were treated with thermal shrinkage. Fifteen patients had involuntary dislocation and four voluntary. The predominant direction of instability was anterior/inferior in 10, posterior in 5 and multiple directions in 4. Patients were followed for a minimum of two years or until surgical failure and recurrence of symptomatology. Postoperatively patients were immobilised in a sling for a period of 3 weeks and were reviewed at 6 weeks and 3, 6, 9 and 12 months and then at six monthly intervals. The Western Ontario shoulder Instability Index was used as a clinical outcome measure as well as subjective and objective evaluation of patient’s function, range of motion, pain and instability.

Results: Nine patients had recurrence of their instability occurring at an average of nine months following their surgical procedure (range 7–14 months). One patient had axillary nerve dysfunction postoperatively with difficulty in abducting the shoulder. Three patients had sensory dysaesthesia related to the axillary nerve territory. All neurological subjective evaluations recovered within 9 months. Four of five patients with a predominantly posterior direction to their instability failed this surgical procedure. Only 2 of 10 (20%) with predominantly anterior instability failed.

Conclusion: Analysis of patients with multidirectional laxity determined that thermal capsulorraphy had a high failure rate (9/19, 47%) with associated significant postoperative complications including axillary nerve dysaesthesias and stiffness.