Asheesh Bedi

The Basic Science of Articular Cartilage: Structure, Composition, and Function

Articular cartilage is the highly specialized connective tissue of diarthrodial joints. Its principal function is to provide a smooth, lubricated surface for articulation and to facilitate the transmission of loads with a low frictional coefficient (Figure 1). Articular cartilage is devoid of blood vessels, lymphatics, and nerves and is subject to a harsh biomechanical environment. Most important, articular cartilage has a limited capacity for intrinsic healing and repair. In this regard, the preservation and health of articular cartilage are paramount to joint health. Figure 1. Gross photograph of healthy articular cartilage in an adult human knee. Injury to articular cartilage is recognized as a cause of significant musculoskeletal morbidity. The unique and complex structure of articular cartilage makes treatment and repair or restoration of the defects challenging for the patient, the surgeon, and the physical therapist. The preservation of articular cartilage is highly dependent on maintaining its organized architecture.

Management of articular cartilage defects of the knee.

Articular cartilage has a poor intrinsic capacity for healing. The goal of surgical techniques to repair articular cartilage injuries is to achieve the regeneration of organized hyaline cartilage. Microfracture and other bone marrow stimulation techniques involve penetration of the subchondral plate in order to recruit mesenchymal stem cells into the chondral defect. The formation of a stable clot that fills the lesion is of paramount importance to achieve a successful outcome. Mosaicplasty is a viable option with which to address osteochondral lesions of the knee and offers the advantage of transplanting hyaline cartilage. However, limited graft availability and donor site morbidity are concerns. Transplantation of an osteochondral allograft consisting of intact, viable articular cartilage and its underlying subchondral bone offers the ability to address large osteochondral defects of the knee, including those involving an entire compartment. The primary theoretical advantage of autologous chondrocyte implantation is the development of hyaline-like cartilage rather than fibrocartilage in the defect, which presumably leads to better long-term outcomes and longevity of the healing tissue. Use of synthetic scaffolds is a potentially attractive alternative to traditional cartilage procedures as they are readily available and, unlike allogeneic tissue transplants, are associated with no risk of disease transmission. Their efficacy, however, has not been proven clinically.

Transtibial versus anteromedial portal reaming in anterior cruciate ligament reconstruction: an anatomic and biomechanical evaluation of surgical technique.

PURPOSE The purpose of this study was to objectively evaluate the anatomic and biomechanical outcomes of anterior cruciate ligament (ACL) reconstruction with transtibial versus anteromedial portal drilling of the femoral tunnel. METHODS Ten human cadaveric knees (5 matched pairs) without ligament injury or pre-existing arthritis underwent ACL reconstruction by either a transtibial or anteromedial portal technique. A medial arthrotomy was created in all cases before reconstruction to determine the center of the native ACL tibial and femoral footprints. A 10-mm tibial tunnel directed toward the center of the tibial footprint was prepared in an identical fashion, starting at the anterior border of the medial collateral ligament in all cases. For transtibial femoral socket preparation (n = 5), a guidewire was placed as close to the center of the femoral footprint as possible. With anteromedial portal reconstruction (n = 5), the guidewire was positioned centrally in the femoral footprint and the tunnel drilled through the medial portal in hyperflexion. An identical graft was fixed and tensioned, and knee stability was assessed with the following standardized examinations: (1) anterior drawer, (2) Lachman, (3) maximal internal rotation at 30°, (4) manual pivot shift, and (5) instrumented pivot shift. Distance from the femoral guidewire to the center of the femoral footprint and dimensions of the tibial tunnel intra-articular aperture were measured for all specimens. Statistical analysis was completed with a repeated-measures analysis of variance and Tukey multiple comparisons test with P ≤ .05 defined as significant. RESULTS The anteromedial portal ACL reconstruction controlled tibial translation significantly more than the transtibial reconstruction with anterior drawer, Lachman, and pivot-shift examinations of knee stability (P ≤ .05). Anteromedial portal ACL reconstruction restored the Lachman and anterior drawer examinations to those of the intact condition and constrained translation with the manual and instrumented pivot-shift examinations more than the native ACL (P ≤ .05). Despite optimal guidewire positioning, the transtibial technique resulted in a mean position 1.94 mm anterior and 3.26 mm superior to the center of the femoral footprint. The guidewire was positioned at the center of the femoral footprint through the anteromedial portal in all cases. The tibial tunnel intra-articular aperture was 38% larger in the anteroposterior dimension with the transtibial versus anteromedial portal technique (mean, 14.9 mm v 10.8 mm; P ≤ .05). CONCLUSIONS The anteromedial portal drilling technique allows for accurate positioning of the femoral socket in the center of the native footprint, resulting in secondary improvement in time-zero control of tibial translation with Lachman and pivot-shift testing compared with conventional transtibial ACL reconstruction. This technique respects the native ACL anatomy but cannot restore it with a single-bundle ACL reconstruction. Eccentric, posterolateral positioning of the guidewire in the tibial tunnel with the transtibial technique results in iatrogenic re-reaming of the tibial tunnel and significant intra-articular aperture expansion. CLINICAL RELEVANCE Anteromedial portal drilling of the femoral socket may allow for improved restoration of anatomy and stability with ACL reconstruction compared with conventional transtibial drilling techniques.

The Management of Labral Tears and Femoroacetabular Impingement of the Hip in the Young, Active Patient

PURPOSE The purpose of this systematic review was to determine (1) the quality of the literature assessing outcomes after surgical treatment of labral tears and femoroacetabular impingement (FAI), (2) patient satisfaction after open or arthroscopic intervention, and (3) differences in outcome with open or arthroscopic approaches. METHODS Computerized literature databases were searched to identify relevant articles from January 1980 to May 2008. Studies were eligible for inclusion if they had a level I, II, III, or IV study design and if the patient population had a labral tear and/or FAI as the major diagnosis. Patients with severe pre-existing osteoarthritis or acetabular dysplasia were excluded. RESULTS Of the 19 articles with reported outcomes after surgery, none used a prospective study design and only 1 met the criteria for level III basis of evidence. Open surgical dislocation with labral debridement and osteoplasty is successful, with a good correlation between patient satisfaction and favorable outcome scores. The studies reviewed support that 65% to 85% of patients will be satisfied with their outcome at a mean of 40 months after surgery. A common finding in all series, however, was an increased incidence of failure among patients with substantial pre-existing osteoarthritis. Arthroscopic treatment of labral tears is also effective, with 67% to 100% of patients being satisfied with their outcomes. CONCLUSIONS The quality of literature reporting outcomes of surgical intervention for labral tears and FAI is limited. Although open surgical dislocation with osteoplasty is the historical gold standard, the scientific data do not show that open techniques have outcomes superior to arthroscopic techniques. LEVEL OF EVIDENCE Level IV, systematic review.

The Effect of Medial Versus Lateral Meniscectomy on the Stability of the Anterior Cruciate Ligament-Deficient Knee

Background: The pivot shift is a dynamic test of knee stability that involves a pathologic, multiplanar motion path elicited by a combination of axial load and valgus force during a knee flexion from an extended position. Purpose: To assess the stabilizing effect of the medial and lateral meniscus on anterior cruciate ligament-deficient (ACL-D) knees during the pivot shift examination. Study Design: Controlled laboratory study. Methods: A Lachman and a mechanized pivot shift test were performed on 16 fresh-frozen cadaveric hip-to-toe lower extremity specimens. The knee was tested intact, ACL-D, and after sectioning the medial meniscus (ACL/MM-D; n = 8), lateral meniscus (ACL/LM-D; n = 8), and both (ACL/LM/MM-D; n = 16). A navigation system recorded the resultant anterior tibial translations (ATTs). For statistical analysis an analysis of variance was used; significance was set at P < .05. Results: The ATT significantly increased in the ACL-D knee after lateral meniscectomy (ACL/LM-D; P < .05) during the pivot shift maneuver. In the lateral compartment of the knee, ATT in the ACL-D knee increased by 6 mm after lateral meniscectomy during the pivot shift (16.6 ± 6.0 vs 10.5 ± 3.5 mm, P < .01 for ACL/LM out vs ACL out). Medial meniscectomy, conversely, had no significant effect on ATT in the ACL-D knee during pivot shift examination (P > .05). With standardized Lachman examination, however, ATT significantly increased after medial but not lateral meniscectomy compared with the ACL-D knee (P < .001). Conclusion: Although the medial meniscus functions as a critical secondary stabilizer to anteriorly directed forces on the tibia during a Lachman examination, the lateral meniscus appears to be a more important restraint to anterior tibial translation during combined valgus and rotatory loads applied during a pivoting maneuver. Clinical Relevance: This model may have implications in the evaluation of surgical reconstruction procedures in complex knee injuries.

Massive Tears of the Rotator Cuff

Repair of massive rotator cuff tears is technically difficult but often feasible. Technical and biological challenges to a successful repair include inelastic poor-quality tendon tissue, scarring, muscle atrophy, and fatty infiltration. Fatty infiltration of the involved rotator cuff muscles has been identified as an important negative prognostic factor for the outcome after repair of massive rotator cuff tears. Tendon transfer is a good option for young patients and manual laborers with an irreparable massive rotator cuff tear. Arthroplasty can be considered for the treatment of symptomatic massive rotator cuff tears in patients who have glenohumeral arthritis.

Radiographic and clinical comparisons of distal tibia shaft fractures (4 to 11 cm proximal to the plafond): plating versus intramedullary nailing.

Objective: The purposes of this study were to review distal tibia shaft fractures treated with a plate or a nail and to assess the clinical and radiographic results, complication rates, and the need for secondary procedures. Design: Retrospective review. Setting: Two Level I trauma centers. Patient/Participants: We retrospectively reviewed 111 patients with 113 extra-articular distal tibia fractures between 4 and 11 cm proximal to the plafond. Seventy-six were treated with an intramedullary nail and 37 were treated with a medial plate. Twenty-nine (27%) of the concomitant fibula fractures were fixed. Main Outcome Measurements: Complications and secondary procedures were evaluated in 111 patients after a mean of 24 months (range, 12-84 months). Results: A total of 111 patients with 113 fractures of the distal tibia were reviewed. Their mean age was 39.1 years, 69% were men, and 30% had open fractures. Four patients underwent additional procedures for soft tissue coverage. None of these had infection. Five patients (4.4%) developed osteomyelitis: four after intramedullary nailing (5.3%) and one after plating (2.7%). Nine patients (12%) had delayed union or nonunion after nailing. One patient (2.7%) had a nonunion after plating (P = 0.10). Nonunion was more common after concurrent fixation of the fibula (14% versus 2.6%, P = 0.04). Angular malalignment of ≥5 degrees occurred in 22 patients with nails (29%) and 2 with plates (5.4%, P = 0.003). Eight patients had malunions of ≥10 degrees. Valgus was the most common deformity (n = 16). Malunion was more common after open fracture (38%, P = 0.006) but was not related to fibula fixation. Painful hardware was removed in six patients (7.9%) with nails and in two patients (5.4%) with plates. Conclusions: Distal tibia fractures may be treated successfully with plates or nails. Delayed union, malunion, and secondary procedures were more frequent after nailing. Randomized prospective assessment may further clarify these issues and provide information about costs associated with these fractures.

Dynamic Contact Mechanics of the Medial Meniscus as a Function of Radial Tear, Repair, and Partial Meniscectomy

BACKGROUND The menisci are integral to normal knee function. The purpose of this study was to measure the contact pressures transmitted to the medial tibial plateau under physiological loads as a function of the percentage of the meniscus involved by the radial tear or repair. Our hypotheses were that (1) there is a threshold size of radial tears above which contact mechanics are adversely affected, and (2) partial meniscectomy results in increased contact pressure compared with that found after meniscal repair. METHODS A knee simulator was used to apply physiological multidirectional dynamic gait loads across human cadaver knees. A sensor inserted below the medial meniscus recorded contact pressures in association with (1) an intact meniscus, (2) a radial tear involving 30% of the meniscal rim width, (3) a radial tear involving 60% of the width, (4) a radial tear involving 90% of the width, (5) an inside-out repair with horizontal mattress sutures, and (6) a partial meniscectomy. The effects of these different types of meniscal manipulation on the magnitude and location of the peak contact pressure were assessed at 14% and 45% of the gait cycle. RESULTS The peak tibial contact pressure in the intact knees was 6 +/- 0.5 MPa and 7.4 +/- 0.6 MPa at 14% and 45% of the gait cycle, respectively. The magnitude and location of the peak contact pressure were not affected by radial tears involving up to 60% of the meniscal rim width. Radial tears involving 90% resulted in a posterocentral shift in peak-pressure location manifested by an increase in pressure in that quadrant of 1.3 +/- 0.5 MPa at 14% of the gait cycle relative to the intact condition. Inside-out mattress suture repair of a 90% tear did not restore the location of the pressure peak to that of the intact knee. Partial meniscectomy led to a further increase in contact pressure in the posterocentral quadrant of 1.4 +/- 0.7 MPa at 14% of the gait cycle. CONCLUSIONS Large radial tears of the medial meniscus are not functionally equivalent to meniscectomies; the residual meniscus continues to provide some load transmission and distribution functions across the joint.

Static and Dynamic Mechanical Causes of Hip Pain

Mechanical hip pain typically has been associated either with dynamic factors resulting in abnormal stress and contact between the femoral head and acetabular rim when the hip is in motion or with static overload stresses related to insufficient congruency between the head and acetabular socket in the axially loaded (standing) position. Compensatory motion may adversely affect the dynamic muscle forces in the pelvic region, leading to further strain and pain. Hip pain related to static overload stresses may also be localized to the anteromedial groin, but compensatory dysfunction of the periarticular musculature may lead to muscular fatigue and associated pain throughout the hip. As our understanding of hip joint mechanics has advanced, it has become increasingly apparent that hip pain in the absence of osteoarthritis may be due to a complex combination of mechanical stresses, both dynamic and static. With an emphasis on findings in the recent literature, this review will describe the dynamic and static factors associated with mechanical hip pain, the combinations of dynamic and static stresses that are commonly identified in hip pain, and common patterns of compensatory injury in patients with femoroacetabular impingement.

Capsular management during hip arthroscopy: from femoroacetabular impingement to instability.

Advances in the ability to treat various soft-tissue and osseous pathologic conditions of the hip arthroscopically have been predicated on an improved exposure of the pathology of the central, peripheral, and peritrochanteric compartments. The management of the capsule is critical and must allow for an improved exposure without compromising stability and kinematics of the hip. Described approaches have included capsulectomy, limited capsulotomy, extensile capsulotomy, capsular plication, and capsular shift. The selected approach must consider various factors, including symptomatic complaints, underlying hyperlaxity, specific mechanical pathology, and surgical expertise. Universally using a single technique without consideration of the complex mechanical and anatomic factors unique to each patient may result in incomplete treatment of the pathoanatomy or iatrogenic instability. This article reviews the anatomy of the hip capsule and provide a diagnosis-based consideration of capsular management during hip arthroscopy. The senior authors preferred techniques are also presented.