Relationship of surgical accuracy and clinical outcomes in Charitè lumbar disc replacement

Abstract

Objective: To retrospectively assess the clinical and functional outcomes of a group of patients receiving Charitè lumbar disc replacement and to compare those outcomes to the corresponding surgical technical accuracy.

Methods: A retrospective study of all patients treated over a 3-year period was undertaken. Objective pain scores were quantified from 1 to 10. Short Form 36-Health Survey (SF-36v2) scores were compared to Australian population norms. Surgical placements were radiographically classified. Heterotopic ossification, disc height restoration and angle-defined instability were assessed using established protocols.

Results: Twenty-five patients were identified with three patients lost to follow-up. Average follow-up was 34 months. Ideal surgical placement was achieved in five (33%) single-level and three (37.5%) dual-level disc replacements. Sub-optimal surgical placement was seen in nine (60%) single-level and five (62.5%) dual-level disc replacements. Poor surgical placement was observed in a single-level disc replacement. All patients demonstrated a reduction in objective pain score (P < 0.05). SF-36v2 outcomes were superior in single-level compared to dual-level and ideal compared to sub-optimal replacements (P < 0.05).

Conclusion: The hypothesis that ideal surgical placements are associated with improved clinical and functional outcomes in total lumbar disc replacement was confirmed.

Figure 1

Radiographic classification of surgical technical accuracy of L4/L5 Charitè disc replacement. Ideal placement was shown in both antero‐posterior (A) and lateral (B) views, with prosthesis located at centroid of both caudal and rostral vertebral bodies. Sub‐optimal placement was demonstrated in both antero‐posterior (C) and lateral (D) views, with the prosthesis centroid offset laterally, but still within manufacturers' guidelines. Poor surgical placement was shown, with prosthesis offset beyond lateral disc “tooth” in antero‐posterior view (E) and posterior to the centroid in the lateral view (F).

Figure 2

Assessment of heterotopic ossification in plain antero‐posterior (AP) radiograph at 36 months post dual‐level L3/L4 & L4/L5 Charitè disc replacement. Radiograph demonstrated circumferential formation (CF) of peri‐prosthetic bone at L4/L5 (Lat radiograph not shown). Unilateral bridging (UB) and marginal osteophytes (O) were visible at L3/L4.

Figure 3

Disc height restoration coefficient and angle defined stability method demonstrated in antero‐posterior (A) and lateral (B) views following dual L3/L4 & L4/5 Charitè disc replacement. Disc height restoration coefficient was calculated by Equation (1).

Figure 4

Objective pain score reduction compared for data grouped according to the number of discs replaced. Pain score reductions were statistically superior for single‐level replacement in comparison to dual‐level replacement (*P < 0.05).

Figure 5

Objective pain score reduction compared for data grouped according to the level of disc replacement. Statistically significant superior reductions demonstrated for L5/S1 compared to L3/L4 (*P < 0.05).

Figure 6

Objective pain score reduction compared for data grouped according to the heterotopic ossification classification. Cases with osteophyte formation, unilateral bridging or bilateral bridging were statistically superior to joints with no formation of peri‐prosthetic bone (*P < 0.05).

Figure 7

Short Form 36‐Health Survey (SF‐36v2) outcomes compared for data grouped according to the number of discs replaced. All SF‐36v2 outcomes (except SF‐36v2 Mental Health) were superior in single‐level replacements compared to dual‐level replacements: statistically significant for Physical Function, Role Physical, General Health, Role Emotional, Physical Health, and Emotional Health (*P < 0.05).

Figure 8

Individual and overall Short Form 36‐Health Survey (SF‐36v2) outcomes compared to SF‐36v2 Australian population norms (SAHOS) for data grouped according to surgical technical accuracy. All SF‐36v2 outcomes were superior for ideal surgical accuracy in comparison to the sub‐optimal surgical placement group; statistically significant for Mental Health, Physical Health, and Emotional Health (*P < 0.05). SF‐36v2 outcomes were superior for ideal placements compared to SAHOS; statistically significant for General Health, Vitality, Role Emotional, Mental Health, Physical Health and Emotional Health (+P < 0.05). Data sourced from: Hawthorne G, Osborne RH, Taylor A, and Sansoni J. The SF36 Version 2: critical analyses of population weights, scoring algorithms and population norms. Quality of Life Research, 2007, 4: 661–673.

Figure 9

Short Form 36‐Health Survey (SF‐36v2) outcomes compared for data grouped according to the heterotopic ossification classification. Statistically significant differences were shown between no formation and unilateral bridging for General Health, Physical Function and Vitality (*P < 0.05) and between osteophyte formation and bilateral bridging for Vitality, Mental Health, Physical Health, and Emotional Health (xP < 0.05).