Animal models of joint contracture may be used to elucidate the mechanisms of arthrofibrosis. Patients with joint contracture commonly undergo surgical capsular release. Previous animal models of joint contracture do not simulate this aspect of arthrofibrosis. We hypothesize that a surgical capsular release will decrease the severity of arthrofibrosis in this rabbit model. A capsular contracture was surgically created in 20 skeletally mature rabbits. Eight weeks later, ten rabbits underwent capsular release, which consisted of elevation of the posterior capsule through a lateral incision and manipulation under anesthesia. Ten rabbits had a sham incision, without release (control group). Immediately after release or sham surgery, extension loss (calculated by subtracting the knee extension angle (degrees) of the operative limb from the nonoperative, contralateral limb) was measured using fluoroscopy. All animals were sacrificed following 16 weeks of postoperative free cage activity. At sacrifice, joint contracture was measured using a custom, calibrated device. The histology of the posterior joint capsule was assessed at sacrifice. All animals survived both operations without complications. Immediately after surgical release or sham surgery, the average extension loss was 129.2 ± 10.7° in the control group versus 29.6 ± 8.2° in the capsular release group (p = 0.0002). Following 16 weeks of remobilization, the average extension loss of the control and capsular release animals were 49.0 ± 12.7° and 36.5 ± 14.2°, respectively (p = 0.035). There were no histological differences between the two groups. In this animal model, a surgical capsular release decreased the extension loss (flexion contracture) immediately after surgery, as well as following sixteen weeks of remobilization. There were no histological changes detected in the posterior joint capsule. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Abstract The relationship between coronal knee laxity and the restraining properties of the collateral ligaments remains unknown. This study investigated correlations between the structural properties of the collateral ligaments and stress angles used in computer-assisted total knee arthroplasty (TKA), measured with an optically based navigation system. Ten fresh-frozen cadaveric knees (mean age: 81 ± 11 years) were dissected to leave the menisci, cruciate ligaments, posterior joint capsule and collateral ligaments. The resected femur and tibia were rigidly secured within a test system which permitted kinematic registration of the knee using a commercially available image-free navigation system. Frontal plane knee alignment and varus-valgus stress angles were acquired. The force applied during varus-valgus testing was quantified. Medial and lateral bone-collateral ligament-bone specimens were then prepared, mounted within a uni-axial materials testing machine, and extended to failure. Force and displacement data were used to calculate the principal structural properties of the ligaments. The mean varus laxity was 4 ± 1° and the mean valgus laxity was 4 ± 2°. The corresponding mean manual force applied was 10 ± 3 N and 11 ± 4 N, respectively. While measures of knee laxity were independent of the ultimate tensile strength and stiffness of the collateral ligaments, there was a significant correlation between the force applied during stress testing and the instantaneous stiffness of the medial (r = 0.91, p = 0.001) and lateral (r = 0.68, p = 0.04) collateral ligaments. These findings suggest that clinicians may perceive a rate of change of ligament stiffness as the end-point during assessment of collateral knee laxity.

The medial collateral ligament complex (MCL) is the most commonly damaged ligamentous stabilizer of the human knee. The diagnostic algorithm comprises patient history, clinical examination and magnetic resonance imaging (MRI). It is important to distinguish between incomplete and complete ruptures of the MCL. For adequate treatment the classification and exact knowledge about concomitant injuries are important. A nonoperative treatment of incomplete ruptures (grades I and II) is widely accepted and usually results in a good clinical outcome but the treatment of complete ruptures (grade III) is a subject of controversy. Complete intraligamentous ruptures with a correct approximation of the stumps and intact dorsomedial joint capsule can also be treated nonoperatively with good and excellent results. In contrast, ruptures close to the abutment and bony avulsions tend to heal better through operative treatment. Dehiscence or dislocation of the ligament stumps in MRI is an indication for operative treatment. In the context of a multiligamentous injury or complex instability, the majority of authors suggest an operative stabilization. As the treatment of chronic instability can be challenging, the initial and adequate treatment of acute ruptures is of great importance.

The aim of this study was to examine the association between different types of exercise loading and femoral neck cross-sectional geometry. Our data comprised proximal femur magnetic resonance (MR) images obtained from 91 female athletes and their 20 age-matched controls. The athletes were categorized according to typical training activity - high impact (high and triple jumping), odd impact (racket and soccer playing), high magnitude (power lifting), repetitive low impact (endurance running) and repetitive non-impact (swimming). Segmented MR images at two locations, narrowest cross-section of the femoral neck (narrowFN) and the cross-section at insertion of articular capsule (distalFN), were investigated to detect between group differences in shape, curvature and buckling ratio derived using image and signal analysis tools. The narrowFN results indicated that the high-impact group had weaker antero-superior (33% larger buckling ratio than controls) but stronger inferior weight-bearing region (32% smaller than controls), while the odd-impact group had stronger superior, posterior and anterior region (21% smaller buckling ratio than controls). The distalFN results indicated that the high-impact group had stronger inferior region (37% smaller buckling ratio), but the odd-impact group had stronger superior region (22% smaller buckling ratio) than the controls. Overall, the results point towards odd-impact exercise loading, with inherently varying directions of impact, associated with more robust cross-sectional geometry along the femoral neck. In conclusion, our one-dimensional polar treatment for geometrical traits and intuitive presentation of differences in trends between exercise groups and controls provides a basis for analysis with high angular accuracy.

Successful tissue engineering strategies for cartilage repair must maximize the efficacy of chondrocytes within their limited life span. To that end, the combination of exogenous growth factors with mechanical stimuli holds promise for development of clinically relevant cartilage tissue substitutes. The current study aimed to determine whether incorporation of transient exposure to growth factors into a hydrodynamic bioreactor system can improve functional maturation of tissue-engineered cartilage. Chondrocyte-seeded polyglycolic acid scaffolds were cultivated within a wavy-walled bioreactor that imparts fluid-flow-induced shear stress for 4 weeks. Constructs were nourished with 100 ng/mL insulin-like growth factor-1 (IGF-1) or 10 ng/mL transforming growth factor-β1 (TGF-β1) either for the first 15 days of the culture (transient) or throughout the entire cultivation (continuous). Transiently treated constructs were found to exhibit better functional properties than continuously nourished constructs. The limited development of engineered tissues continuously stimulated by IGF-1 or TGF-β1 was related to massive growth factor leftovers in the environments which down-regulated the expression of the associated receptors. Treatment with TGF-β1 eliminated the formation of a fibrous capsule at the construct periphery possibly through suppression of Smad3 phosphorylation, yielding constructs with greater homogeneity. Furthermore, TGF-β1 reversely regulated Smad2 and Smad3 pathways in articular chondrocytes under hydrodynamic stimuli partially via Smad7. Collectively, transient exposure to growth factors is likely to maintain chondrocyte homeostasis and thus promotes their anabolic activities under hydrodynamic stimuli. The present work suggests that robust hydrodynamically engineered neocartilage with a reduced fibrotic response and enhanced tissue homogeneity can be achieved through optimization of growth factor supplementation protocols and potentially through manipulation of intracellular signals such as Smad.

BACKGROUND

AND

HYPOTHESIS:

Rotator cuff tears are the most common injury seen by shoulder surgeons. Glenohumeral osteoarthritis develops in many late-stage rotator cuff tear patients as a result of torn cuff tendons, termed "cuff tear arthropathy." However, the mechanisms of cuff tear arthropathy have not been fully established. It has been hypothesized that a combination of synovial and mechanical factors contribute equally to the development of cuff tear arthropathy. The goal of this study was to assess the utility of this model in investigating cuff tear arthropathy.

MATERIALS AND METHODS:

We used a rat model that accurately reflects rotator cuff muscle degradation after massive rotator cuff tears through either infraspinatus and supraspinatus tenotomy or suprascapular nerve transection. Using a modified Mankin scoring system, we found significant glenohumeral cartilage damage after both rotator cuff tenotomy and suprascapular nerve transection after only 12 weeks.

RESULTS:

Cartilage degeneration was similar between groups and was present on both the humeral head and the glenoid. Denervation of the supraspinatus and infraspinatus muscles without opening the joint capsule caused cartilage degeneration similar to that found in the tendon transection group.

CONCLUSIONS:

Our results suggest that altered mechanical loading after rotator cuff tears is the primary factor in cartilage degeneration after rotator cuff tears. Clinically, understanding the process of cartilage degeneration after rotator cuff injury will help guide treatment decisions in the setting of rotator cuff tears.

OBJECTIVES:

The aim of this retrospective study was to measure the inferior glenohumeral capsule thickness of shoulders clinically affected by capsular contracture by comparison to the contralateral asymptomatic side.

METHODS:

Bilateral shoulder ultrasound (US) examinations of 20 patients with clinically or MRI proven unilateral capsular contracture were retrospectively assessed. Inferior capsule evaluation was performed with a transducer placed within the axilla in maximally abducted shoulders. Measurements were symmetrically performed orthogonally to the inferior glenohumeral ligament (IGHL) in the axial plane; the coronal plane was used to ensure the tension of the IGHL. The significance of any difference in thickening was assessed with the Mann-Whitney test.

RESULTS:

The average thickness was 4.0 mm in shoulders with capsular contracture vs. 1.3 mm in asymptomatic contralateral shoulders (P < 0.0001). Twenty per cent of patients with capsular contracture and inferior capsule thickness increase showed US features of other painful diseases of the rotator cuff.

CONCLUSION:

The thickness of the inferior capsule is measurable through ultrasound examination and appears to be increased in shoulders with capsular contracture. Exploration of the inferior aspect of the shoulder joint could be added to shoulder US examination protocols for capsular contracture assessment even if other rotator cuff abnormalities are diagnosed by US. KEY POINTS: • Ultrasound is increasingly used to diagnose shoulder problems. • The thickness of the inferior glenohumeral ligament is measurable in the axilla. • The inferior glenohumeral ligament appears thickened in shoulders with capsular contracture. • Capsular contracture ultrasound features can be associated with other rotator cuff problems.

INTRODUCTION,

OBJECTIVE:

Gait analysis has provided important information about the variability of gait for patients prior to and after total hip arthroplasty (THA). The objective of this research was to clarify how the method of exposure in total hip arthroplasty affects the variability of gait. MATERIALS AND

METHOD:

Gait analysis was performed at 0.8m/s, 1.0m/s, and 1.2m/s on 25 patients with direct-lateral exposure (DL), 22 with antero-lateral exposure (AL) and 25 with posterior exposure (P) during total hip arthroplasty. The control group was represented by 45 healthy subjects of identical age. Gait analysis was performed pre-operatively and 3 and 6months after the surgery. Gait parameter variability was characterized by the coefficient of variance (CV) of spatial-temporal parameters and by the mean coefficient of variance (MeanCV) of angular parameters.

RESULTS:

The variability of gait tends to reach control values during the first 6months of the postoperative period in all three patient groups. Six months after THA, in patients operated with DL and AL exposure the variability of gait differs significantly from control values; however, in patients operated with P exposure, the variability of spatial-temporal and angular parameters - except the rotation of pelvis - was similar to that of controls. DISCUSSION,

CONCLUSION:

The type of surgical technique significantly influences the variability of gait. Difference in the variability of angular parameters predicts gait instability and increased risk of falling after THA without the joint capsule preserved. Joint capsule preservation ensures a recovery of gait variability. It should be taken into account when compiling rehabilitation protocols. Differences related to the method of exposure should be considered when abandoning therapeutic aids.

The distal saphenous nerve is commonly known to provide cutaneous innervation of the medial side of the ankle and distally to the base of the great toe. We hypothesize that the saphenous nerve innervates the periosteum of the medial malleolus and joint capsule.Five fresh limbs were dissected and the saphenous nerve was traced distally with magnification. The medial malleolus, talus, and soft tissue were fixed in formaldehyde, decalcified, and embedded in paraffin and sectioned. Histologic slides were then prepared using S100 antibody nerve stains.Histologic slides were examined and myelinated nerves could be observed within the medial capsule and periosteum in all the specimens.We have demonstrated that the saphenous nerve innervates the periosteum of the medial malleolus and joint capsule.

Synovial osteochondromatosis is a rare, benign condition characterised by synovial metaplasia and the formation of cartilaginous and osteocartilaginous bodies in the capsule. We report one such case in a 30-year-old woman with synovial osteochondromatosis of the hip and progressive osteoarthritis caused by femoroacetabular impingement with joint-space narrowing. She underwent surgical removal of 32 loose bodies and osteochondroplasty. A coronal osteophyte at the junction of the femoral head and neck was also excised. At 2-year follow-up, her Harris Hip Score had improved from 62 to 90.