Dana C. Mears

Displaced acetabular fractures managed operatively: indicators of outcome.

This study examined retrospectively the clinical and radiographic features of acute displaced acetabular fractures which heavily influence the quality of an open reduction and clinical outcome. Of 424 acute fractures (119 simple and 305 associated injuries) in 411 patients, the mean time from the injury to surgery was 8.2 days (range, 0–21 days). The mean age of the patients was 46.5 years (range, 13–89 years), and followup was an average of 9.3 years (range, 3–21 years). For the 424 hips, the reduction was anatomic in 282 (67%), imperfect in 90 (21%), poor in 39 (9%), and secondarily congruent in 13 both-column fractures (3%). The quality of the reductions markedly deteriorated with advancing age. Clinically, the Harris hip score was excellent in 179 (42%), good in 126 (30%), fair in 54 (13%), and poor in 65 (15%). Excellent or good clinical outcomes were recorded in 249 of 282 patients (89%) with an anatomic reduction. Of the 119 patients with fair and poor results, 92 patients (77%) had complicating factors recognizable at clinical presentation, including extensive impaction, articular abrasion, a femoral head or neck fracture, or endogenous obesity. Although stable anatomic reduction of most displaced acetabular fractures affords the optimal prognosis, especially in younger patients, the initial clinical and radiologic evaluations delineate a sizable minority with poorly prognostic features that favor a poor clinical outcome after internal fixation, by minimizing the likelihood for an anatomic reduction or compromising the outcome despite an anatomic reduction. With the rapidly aging population accentuating this trend, a reappraisal for the role of the current therapeutic alternatives of nonoperative treatment, a limited open reduction, or an acute total hip replacement merits review.

The Role of Free-Tissue Transfers in Lower-Extremity Reconstruction

Eighty-five free flaps were performed in 76 patients for defects in the lower extremity. A new classification of lower-extremity defects was devised to help define the role of free-tissue transfers: group 1, soft-tissue defects; group 2, soft-tissue and bone loss less than 8 cm; group 3, massive soft-tissue and bone loss greater than 8 cm; and group 4, bone defect only. Each group was further divided into clean (A) and infected (B) wounds. Our overall results include resolution of the presenting problem in 82 percent; there were 17 flap losses (20 percent), persistent osteomyelitis in 8, and 10 amputations. This review has prompted us to limit our indications for limb salvage, particularly in group 3B, in patients with compound injuries that include loss of plantar sensation, and in patients with large segments of infected bone.

The results of 39 fractures complicated by major segmental bone loss and/or leg length discrepancy.

Thirty-nine fractures with segmental bone loss and/or limb length discrepancy with defects of 1.8 to 12.0 cm were reviewed retrospectively. Most patients presented with an acute open fracture with segmental bone loss or a late reconstructive problem with a nonunion, frequently complicated by infection, segmental bone loss, and adjacent soft-tissue disruption. One hundred forty-two weeks was the average length of time of treatment before referral of a patient to us. Eighty-eight per cent of the patients received a bone graft that included either autologous cancellous bone, bank bone, a vascularized free iliac crest or fibular transplant, or some combination of these materials. Forty per cent of the patients required some type of soft-tissue coverage such as a split-thickness skin graft, myoplasty, or a free vascularized flap. Seventy-nine per cent of the cases achieved complete osseous and soft-tissue healing within an average of 49 weeks. One patient underwent an above-knee amputation. Almost 80% of all of the patients healed to within 85% or better of anatomic length. Based upon these results a protocol for the management of osseous and soft-tissue defects is outlined which includes debridement, rigid stabilization, and various types of soft-tissue and osseous reconstruction.

Modern concepts of external skeletal fixation of the pelvis

The treatment of unstable pelvic ring fractures, markedly comminuted and displaced acetabular fractures and combinations of these insults to the pelvis is an unsolved problem. Of all the previously described methods, external fixation has appeared to hold the most promise for certain pelvic bone injuries of major proportions which are accompanied by instability of the pelvic ring. Many of the external fixation devices of the past have not provided adequate stability. A modification of the Hoffmann external frame provides a simple method of treatment for unstable pelvic ring fractures that immediately permits the patient to move from bed to chair. Complex pelvic and central acetabular fractures also are responsive to treatment by extensive external frames. While this external skeletal fixation is superior to previously available devices, internal fixation is under consideration for stabilization of the posterior portion of the pelvic ring. A combination of internal and external fixation may also be advantageous for severely disrupted pelvic bones.

Comparative mechanical performances of some new devices for fixation of unstable pelvic ring fractures

A laboratory cadaveric model, developed previously for the study of currently employed external fixation devices used for unstable pelvic fractures was used to evaluate rigidity improvements associated with a number of fixation design innovations. Based on quasistatic shearing displacements measured at the sacro-iliac joint and symphysis pubis disruption sites, otherwise identical anterior frameworks constructed on 5 mm fixation halfpins, rather than upon standard 4 mm halfpins, were able to sustain markedly (58% to 210%) greater loadings. A new and very simple traingular framework was designed and constructed for which the fixation rigidity was found to rival that of much more complex and cumbersome double anterior frames. When used as the posterior component of combined anterior/posterior fixation systems, a new double cobra-type (internal) plate allowed the injury model pelvises to sustain near-physiological load levels. A pair of dynamic compression plates attached across a disrupted symphysis pubis was found to be a biomechanically acceptable substitute for an anterior external fixator.

Release of neutral proteinases from mononuclear phagocytes and synovial cells in response to cartilaginous wear particles in vitro

Cartilaginous wear particles were retrieved from synovial fluid aspirates of human diarthrodial joints and added to cultures of human or murine mononuclear phagocytes or human synovial cells. In each case, addition of the wear particles elevated the production of proteinases active at neutral pH against collage, gelatin, azocasein and the synthetic pentapeptide phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg. Synovial cells secreted more than five times as much collagenase as the same number of the other cells. All types of cell secreted significant quantities of enzymes active against the noncollagenous substrates. Mild treatment of the spent media with trypsin stimulated all of these eurmymic activities. The spent culture media of synovial cells which had been exposed to cartilaginous wear particles released hydroxyproline and glycosaminoglycan from powdered cartilage, indicating the production of enzymes which degrade both the collagen and proteoglycan of th cartilaginous matrix. Cultures of mononuclear phagocytes, in contrast, while solubilizing chondroitin sulphate from cartilage, released very little hydroxyproline. The ability of wear particles to elicit these effects suggests a role for them in the pathogenesis of osteoarthritis and other types of joint deterioration.

Stability of acetabular fractures after internal fixation: A cadaveric study

The rigidity of a transverse acetabular fracture in a laboratory cadaveric model immobilized by internal fixation was studied. On the application of a longitudinal load imposed on the fifth lumbar vertebra, four modes of displacement of the acetabular fracture were monitored by the use of variable impedance transducers. The rigidity of various combinations of lag screws and plates was assessed. The fracture deformations documented were generally quite small at any observation point with any of the fixation methods, and in most cases they were recoverable on load release. Anterior column lag screw fixation combined with plate fixation of the posterior column provided a degree of stability indistinguishable from that of other methods, and allowed the minimal exposure and devascularization of the pelvis. The 3.5 mm reconstruction plate, which is readily contoured to the intricate peri-acetabular bony structure, showed no significant difference in rigidity compared to the other apparently more rigid plates under study.

External fixation of unstable pelvic ring fractures: comparative rigidity of some current frame configurations

The effectiveness of external fixation in the stabilisation of pelvic ring fractures was studied in a laboratory cadaveric series. Shearing displacements occurring at sacroiliac joint and symphysis pubis dislocation sites, due to simplified longitudinal loading of the sacrum in an Instron unit, were monitored using variable-impedence transducers. The rigidity of fixation was compared for the Slätis and the Bonnel single anterior frames, for coupled and uncoupled double anterior frames, and for combined anterior-plus-posterior fixation achieved with separate transfixation pin clusters, with through-and-through pin clusters, or with a posterior screw plate. The data showed that the use of posterior fixation provided greatly enhanced stabilisation compared to that achieved with anterior fixation alone. The complex double anterior frames performed only slightly better than did the simpler single anterior frames. In no case, however, was it possible to recover rigidity levels approaching those of the intact pelvis. The results suggest that the transfixation pin arrangement is the most important determinant of pelvic fixation stability, and that further investigation of posterior screw-plate fixation is warranted.

Treatment of Chronic Infected Hip Arthroplasty Wounds by Radical Debridement and Obliteration with Pedicled and Free Muscle Flaps

Nine patients with extensive wounds of the hip joint due to chronic infection following total hip arthroplasty or internal fixation of fractures of the femoral head and neck have been treated by serial radical debridements to remove infected bone, contaminated remnants of bone cement, and the surrounding fibrotic soft tissues. The resultant deep cavity extending down to the acetabulum has then been obliterated with either pedicled muscle flaps or free muscle flaps. Subcutaneous or transpelvic transposition of rectus abdominis muscle flaps is preferred for smaller defects, but only the free latissimus dorsi muscle flap provides sufficient volume of tissue to obliterate the more extensive hip defects. Systemic antibiotics have been continued only for a short-term course of 14 days postoperatively. There has been no recurrence of infection, with follow-up ranging between 6 months and 3° years. One patient has undergone reimplantation of a second custom hip prosthesis into the vascularized bed of a free latissimus dorsi muscle flap.

Ferrography: Its application to the study of human joint wear

Abstract Synovial fluid aspirates of 20 arthroplastic and 150 osteoarthritic joints were analyzed for evidence of wear particles. Ferrography, an industrial technique for the separation of particulate matter from samples of lubricating solutions, allows extraction of wear particles from synovial fluid. Bichromatic polarized microscopy and scanning electron microscopy permit identification and characterization of metallic, polyethylene and acrylic wear particles from arthroplastic joints as well as biological wear fragments of bone, cartilage, meniscus and synovium from osteoarthritic joints. With both techniques, the number and morphology of the wear particles within the synovial fluid specimens correlate with the rate and mechanism of wear as confirmed by examination of the joint implant or articular surfaces. Toxicity of the various types of wear particles was assessed by cytological examination of the fluid aspirate. Of significant interest is the identification of active phagocytosis of wear particles by synovial fluid white blood cells. This finding may implicate the particles as initiators of secondary inflammatory responses, as occurs in other arthritic diseases. Analysis of aspirated synovial fluid appears to be a useful method for studying the rates, mechanisms and biological responses to wear in both arthroplastic and degenerative joints. In surgical joint replacement, this technique holds much promise, not only as a test for wear and toxicity, but also as a means of assisting in the selection of materials and designs for superior articular implants. In osteoarthritic joints, this analysis provides a method for early diagnosis, serial assessment of therapy and prognostication concerning the future course of the disease. Possibly of most significance, in contrast to previous studies on intact articular surfaces, is the ability to study the principal site of degenerative changes, namely the wear particles. This ability may aid in the elucidation of the underlying cause of osteoarthritis.