HETEROTOPIC OSSIFICATION FOLLOWING PRIMARY TOTAL KNEE ARTHROPLASTY

Ninety-eight consecutive primary total knee arthroplasties (TKAs) in 7 0 patients were retrospectively evaluated for heterotopic ossification (HO). A radiographic classification was devised based on the extent a nd location of the ectopic bone. Twenty-five knees (26%) in 19 patient s developed HO. Eight of 11 patients (73%) with preexisting heterotopi c bone at other sites developed HO in the index knee. Multivariate ana lysis demonstrated that advanced HO was associated with restricted kne e motion. Eight knees with advanced HO had a mean 14 degrees decrease in postoperative, as compared with preoperative, knee flexion (P < .05 ). For all patients with HO, mean lumbar spine bone mineral density (B MD) was significantly elevated compared with a matched control group n ot developing HO (P < .05). Heterotopic ossification following primary TI(A correlates with a Limitation of postoperative knee flexion and i s predicted by increased lumbar BMD. Preoperative measurement of spina l BMD may identify those patients at risk for HO and allow for the ins titution of preoperative prophylaxis and modification df postoperative rehabilitation to optimize functional outcome following TKA.