Catastrophic failure of the acetabular component in a ceramic-polyethylene bearing total hip arthroplasty.

Recent research in total hip arthroplasty has focused on attempts to decrease wear at the femoral head-acetabulum articulation, to limit the production of debris that is believed to lead to osteolysis and prosthetic loosening. The use of ceramic-on-polyethylene bearing surfaces has been reported to produce lower wear rates and therefore may increase the life expectancy of the joint arthroplasty. Problems with this bearing have been reported to be due to ceramic femoral head fracture. Reported here are 2 cases of catastrophic failure of total hip arthroplasties, involving a ceramic femoral head, caused by failure of the polyethylene acetabular liner, with subsequent penetration of the femoral head through the acetabular shell.

The use of somatosensory evoked potentials for detection of neuropraxia during shoulder arthroscopy.

With the increase in the use of shoulder arthroscopy in the past decade, there has been an increased awareness of complications. Reports of the occurrence of transient neuropraxia indicate an incidence of 10%-30%. The recording of somatosensory evoked potentials (SEP) for the study and functional monitoring of the sensory pathway is well accepted as a reproducible method of monitoring peripheral nerve and spinal cord function during surgery. SEPs were recorded during shoulder arthroscopy in 20 patients to monitor the musculocutaneous nerve, ulnar nerve, and either the median or radial nerve. In all 20 cases, abnormal SEPs of the musculocutaneous nerve were demonstrated. In 16 cases, this was produced upon initial joint distention, and in 15 cases, by traction; in 11, by longitudinal traction of greater than or equal to 12 lb, and in six by perpendicular traction of greater than or equal to 7 lb. In 10 patients, there were varying combinations of median, ulnar, and radial nerve involvement. There were two cases of clinical neuropraxia in this series. One resolved in 24 h and one in 48 h. The conclusion is that there is a real potential for neurologic damage during shoulder arthroscopy and that the musculocutaneous nerve is the most vulnerable. Factors responsible include joint distention, excessive traction, and extravasation of fluid. The use of SEPs provides a reliable means for monitoring the neurologic status of the extremity during shoulder arthroscopy.

Axial malalignment in femoral neck fractures. An experimental study.

Varus, valgus, and retroversion-anteversion displacements of femoral neck fractures are easily identified on standard AP and lateral radiographs, but rotational malalignments are frequently overlooked. Alterations of the normal appearance of the trabecular systems will indicate rotatory malalignments. A misleading picture of what seems to be severe osteoporosis may actually be due to malrotation and disappearance of the normal trabecular pattern on radiograph.

Results of total knee replacement using an uncemented tibial component.

Fourteen patients (16 knees) underwent total knee arthroplasty with a noncemented tibial component. Clinical evaluation at one year and two years showed a level of function and pain relief comparable to that reported in studies of cemented prostheses. Radiographic studies demonstrated evidence of active bone implant consolidation.